The Large Sky Area Multi-Object Fiber Spectroscopic Telescope (LAMOST) has helped Gaia achieve millimagnitude (mmag) precision in photometry, according to a study led by researchers from National Astronomical Observatories of Chinese Academy of Sciences (NAOC) and Beijing Normal University (BNU).
If you look at the sky on a clear, starry night, you may notice that Aldebran is relatively red and Rigel is blue. Why? The answer stems from their intrinsic physical properties. Precisely measuring magnitudes and colors helps to explain such phenomena.
The ESA Gaia satellite is well known for its remarkable capacity for astrometric observation. It delivers the most precise photometric data ever, with much higher quality than ground-based telescopes.
However, in order for Gaia to cover a wide magnitude range from 6 to 22 magnitude (mag), different observation modes have been adopted for stars of different brightness. In addition, photometric data in the G, BP, and RP bands come from different instruments and CCDs. Therefore, magnitude and color-dependent systematic errors exist.
The researchers combined two datasets, Gaia Data Release 2 (DR2) and LAMOST Data Release 5 (DR5), then selected samples of high data quality and low extinction.
The samples comprised 779,691 main-sequence stars and 71,952 red giant branch stars. Stars from 13.3 to 13.7 mag in the G band were selected as the control sample in order to establish the empirical relationship between intrinsic colors and physical parameters deduced from LAMOST.
“Applying the relationship to the whole sample, the differences between the observed colors and model-determining colors at different G magnitudes represent the color correction terms,” said Prof. LIU Jifeng from NAOC.
With the help of LAMOST’s massive stellar spectrum, the researchers used a spectroscopy-based stellar color regression method to correct systematic errors that are magnitude- and color-dependent. The relationship between the intrinsic colors and physical parameters of stars represents the key focus of this method.
By using a sample of about 500,000 stars from LAMOST and Gaia, color correction curves for the F/G/K stars are derived. “With an unprecedented precision of about 1 mmag, systematic trends in the G magnitude are revealed for both G-RP and BP-RP colors in detail,” said Prof. YUAN Haibo from BNU, the corresponding author of the study.
“Our work could be beneficial to studies where a high-precision color-color diagram is required, including the estimation of Gaia photometric metallicities, detection of peculiar objects, discrimination between binaries and single stars, and so on,” said NIU Zexi, Ph.D. candidate from NAOC and lead author of the study.
Featured image: Schematic illustration of the spectroscopy-based stellar color regression method. (Image by NIU Zexi)
Reference: Zexi Niu, Haibo Yuan, and Jifeng Liu, “Correction to the Photometric Colors of the Gaia Data Release 2 with the Stellar Color Regression Method”, The Astrophysical Journal, 909(1), 2021. Link to paper
TANG Zehao from Yunnan Observatories of the Chinese Academy of Sciences, and his collaborators firstly reported sympathetic standard and blowout coronal jets from two nearby coronal bright points in a polar coronal hole. The study was published in The Astrophysical Journal Letter.
Coronal jets, mainly triggered by the magnetic reconnection, are very pervasive in the solar atmosphere. They are heated plasmas flows moving along magnetic field lines showing as collimated or two-sided ejections. Solar jets are a ubiquitous phenomenon in the solar atmosphere. They may be the potential explanation for solar wind and even spicules, and are usually triggered by the internal magnetic activities, i.e., magnetic emergences and cancellations.
Besides solar jets, there exist many kinds of successive solar eruptions during a relatively short time interval in the solar atmosphere. These phenomenon occurring at different sites and showing internal physical connections were called sympathetic eruptions. Before then, sympathetic eruptions among the wave and filament, different flares, different coronal mass ejections (CMEs) and different filaments have been reported, but sympathetic solar jets have not yet.
To investigate the sympathetic solar jets, the researchers diagnosed two successive coronal jets occurring in the south polar coronal hole on March 31, 2019, using data of X-ray, extreme ultraviolet wavelengths, and photospheric magnetograms.
In this event, two jets emanated from two adjacent coronal bright points (CBP1 and CBP2) successively. The first jet (jet1) was characterized by a typical inverted-Y (or cusp) and its lateral motion, suggesting that it was a standard jet and triggered by the magnetic reconnection between CBP1 and ambient field. The second jet (jet2) erupted successively after the first jet impinged upon its nearby CBP2. The trigger of jet2 is observationally evidenced to be the magnetic reconnection between jet1 and CBP2, suggesting that these two successive jets are connected with each other physically.
In addition, the researchers found a strong twisted structure within jet2’s base, which eventually erupted, resulting in the dramatically brightening of the jet base and the broadening of the jet spire. Thus, the second jet is a blowout jet. Therefore, these two successive jets are sympathetic standard and blowout jets.
This study indicates that besides the internal triggers, coronal jets can be triggered by external eruptions or disturbances.
Reference: Zehao Tang, Yuandeng Shen et al., “Sympathetic Standard and Blowout Coronal Jets Observed in a Polar Coronal Hole”, The Astrophysical Journal Letters, 912(1), 2021. Link to paper
A study published in The Astrophysical Journal and mainly by Dr. CAI Qiangwei from Luoyang Normal University and Dr. YE Jing from Yunnan Observatories of the Chinese Academy of Sciences reported the numerical work about the supra-arcade fans (SAFs). The findings implied that the formation and evolution of the SAF is related to the turbulence in the flare current sheet.
It is found in many observations that a distributed structure named as supra-arcade fan exists above post-flare loops in solar eruptions. The location of the SAF is spatially consistent with various emission sources. Termination shocks (TSs) that are often regarded as an efficient driver for particle acceleration possibly exist in the SAF.
In order to study the thermodynamical manifestations of the SAF, and the potential detection of TSs in extreme ultraviolet (EUV) images, the researchers performed the high-resolution magnetohydrodynamical (MHD) simulations based on the standard flare model with thermal conduction and radiative cooling. The results showed that the SAF is formed by the reconnection outflows, and it starts oscillating when the tearing mode develops.
Using the streamline tracking method, they found that the motion history and temperature evolution of plasmas inside the SAF indicated that the mass of the SAF comes from the corona, and the plasmas are heated in the reconnecting current sheet.
Besides, the researchers found that the height of the SAF undergoes a decent-ascent trend during the impulsive and the decay phases, which could be explained by the unbalance of the Lorentz force and the pressure force inside the magnetic loops. The motion of the SAF probably explains the observed motion of the hard X-ray sources.
Based on the synthetic EUV images, they showed that TSs are possibly identified in Atmospheric Imaging Assembly wavelengths under some observational conditions. For instance, due to the projection effect and the limitation of observational instrument, the shock surface could change from vertical to tilted in the realistic situation, resulting in the unobvious characteristics of TSs.
This study helps people to better understand the details hidden in the SAF and provides some flexible ways to demonstrate the theory in the future.
Reference: Qiangwei Cai, Hengqiang Feng et al., “Dynamical and Thermal Manifestations of the Region above the Top of the Post-flare Loops: MHD Simulations”, Astrophysical Journal, 912(1), 2021. Link to paper
A small drug molecule that appears to protect normal tissue from the damaging effects of radiation, may simultaneously be able to boost the cancer-killing effect of radiation therapy, according to a new study led by scientists at University of Iowa, University of Texas Southwestern Medical Center, and Galera Therapeutics, Inc.
The study, published online May 12 in Science Translational Medicine, suggests that the drug’s dual effect is based on a fundamental difference between the ability of cancer cells and healthy cells to withstand the damaging effects of a highly reactive molecule called hydrogen peroxide, which is produced during the dismutation of superoxide.
The drug, known as Avasopasem manganese, is made by Galera Therapeutics. It acts like a natural enzyme called superoxide dismutase and converts superoxide into hydrogen peroxide. Based on its ability to “mop up” damaging superoxide molecules, which are produced by radiation treatment, the drug is currently in clinical trials to test its ability to protect mucosal tissue from the side-effect of radiotherapy.
Since radiation generates large amounts of superoxide, combining the drug with radiation therapy can generate high levels of hydrogen peroxide. This does not harm normal tissue because healthy cells have metabolic systems that remove hydrogen peroxide. In contrast, cancer cells, which are biologically abnormal, can be overwhelmed by high levels of hydrogen peroxide.
“Cancer cells and healthy cells respond very differently to the increased amount of hydrogen peroxide,” says Douglas Spitz, PhD, UI professor of radiation oncology and co-lead author of the study. “Our study shows that Avasopasem manganese interacts synergistically with high doses of radiation to create hydrogen peroxide that selectively kill cancer cells but is relatively harmless to normal tissue.”
The study showed that in mouse models of lung and pancreatic cancer the drug synergized with radiotherapy to such an extent that the treatment was able to destroy the tumors. The study also showed the greatest synergy occurred with high daily dose radiotherapy, similar to the doses delivered with Stereotactic Body Radiation Therapy (SBRT) currently used to treat some patients with cancer.
The researchers used several experiments to confirm that hydrogen peroxide was the key component in the synergistic effect. They showed the effect was blocked by adding in an enzyme that removes hydrogen peroxide and was enhanced when hydrogen peroxide breakdown was prevented.
“These findings are the result of collaborative efforts over several years by scientists primarily at Iowa, UT Southwestern Medical Center, and Galera, and are already being translated into several ongoing clinical studies,” adds Spitz, who is a member of Holden Comprehensive Cancer Center at the UI. “One of those early phase trials recently reported that Avasopasem manganese in combination with high daily dose radiotherapy appears to nearly double overall survival in patients with pancreatic cancer compared to a placebo plus the same radiotherapy. Our study lays out the novel scientific basis for this potentially ground-breaking therapy for patients.”
In addition to Spitz, the study team included co-lead author Michael Story, PhD, at UT Southwestern Medical Center, and colleagues at UI, UT Southwestern Medical Center, and Galera Therapeutics, Inc.
The research was funded in part by grants from the National Cancer Institute and a sponsored research agreement with Galera Therapeutics.
All images credit: University of Iowa
Reference: Brock J. Sishc, Lianghao Ding, “Avasopasem manganese synergizes with hypofractionated radiation to ablate tumors through the generation of hydrogen peroxide”, Science Translational Medicine 12 May 2021: Vol. 13, Issue 593, eabb3768 DOI: 10.1126/scitranslmed.abb3768
They had the European Xmm-Newton space telescope at their disposal for three million seconds. Objective: to observe and study an ultra-selected sample of 118 galaxy clusters. They are the astronomers of the Chex-Mate project. Now that the observations draw to a close, their first scientific articles are starting to come out. We talk about it with Stefano Ettori of INAF of Bologna, principal investigator of the project together with Monique Arnaud of Cea
Astronomers are somewhat archaeologists, it is often said: the farther they look, the more they go back in time. But astronomers are also somewhat demographers: they study populations of stars and observe how they live, how they are distributed, how they congregate. In small or large cities – the galaxies – with a bustling center of activity, sometimes surrounded by small satellite cities and with arteries of gas – the filaments – connecting them to each other. Galaxies, in turn, congregate into larger structures, the largest in the universe: clusters of galaxies. And it is to study the properties of these clusters that the astronomers of the Chex-Mate projecthave obtained, since 2018, three million seconds of observing time with one of the best space telescopes for X-rays, the Xmm – Newton satellite of the European Space Agency.
“Three million seconds that we are running out in these days; by the summer we should finish all the observations “, Stefano Ettori of INAF OAS of Bologna told Media Inaf , who together with Monique Arnaud of the Cea of the scientific pole of Paris-Saclay, in France, is leading the team of about eighty astronomers (about a quarter of which from INAF, distributed among the offices of Bologna, Florence, Milan, Trieste, Padua), from eleven different states, participating in the project. With the observations now at the end, the first works are in production. Among these an article coming out on Astronomy & Astrophysics in which the demographic characteristics – in fact – of the population of clusters under observation are described in detail.
Hector, why are you astronomers so interested in clusters?
“First of all because they represent the largest structures that have collapsed in the universe. They collapsed under the action of gravity on megaparsec scales, or dimensions of a few million light years. There the action of gravity manifests its full effectiveness in assembling the most extreme – that is, the most massive – bound structures that our theories tell us can be formed. And representing the “extreme” population they are “extremely” sensitive to the initial ingredients that describe these theories. In other words, if the total mass had been different, or if the expansion of the universe was due to dark energyhad it been slowed down or occurred at different times, this would have altered the balance between the collapsing mass and the expanding universe, producing, for example, a different number of galaxy clusters. Therefore, simply counting these clusters already offers direct information on what are the fundamental ingredients of the universe and on their “doses”: how much baryon matter (ie gas and stars), how much dark matter, and how much dark energy ».
So counting how many have been able to reconstruct what the universe is like?
“How it is made and what its initial conditions were, when it started to evolve and form structures. But there’s more: being the largest structures, the clusters are easy to spot. Not only that: being relatively rare – very rare compared to galaxies – it is much easier to count the clusters than to count the single galaxies in the universe. And counting them, doing some statistics on their distribution in the sky and on how many have formed at different masses, we can go back to the initial conditions of the universe when the law that regulates the formation of these structures came into action. “.
Is it a bit like what cosmologists do when they go to count and measure the size of the dots on the CMB map, the radiation of the cosmic microwave background?
“Exactly. On the other hand, the “dots” of the Cmb are fluctuations, in the order of a few tens of microkelvins, with respect to the average temperature of 2.7 kelvins. Some of these points, among the best defined, are clusters of galaxies, which can sometimes appear linked together in even larger structures, called superclusters , which are expected to collapse in the distant future. But at the present time, among the structures that have energy within them distributed in a balanced way, the largest are the clusters of galaxies. This is why they are important to study. Not only that: once formed, they are like small universes ».
What do you mean?
“Having isolated themselves from the expansion of the universe, they have made a home to themselves. If we equated galaxies with cities, clusters would be states. It therefore becomes interesting to study how a state governs itself – and not all states are the same. This is the sense of Chex-Mate : in practice it is a “demographic” champion. We reconstructed the geography of the clusters and went to sample the population of the various “states” – something that had never been done in such a homogeneous way ».
And you did it, I see, by looking at its X-ray emission. How do clusters generate X-rays?
“What happens is that in ionized plasma – therefore with electrons and protons separated from each other – when an electron passes next to a proton its trajectory is deflected and its speed slowed down, thus giving rise to the phenomenon of bremsstrahlung , or braking radiation. . If the energy of the electrons is high enough, as is the case with baryonic matter falling into clusters – this radiation is emitted in the X-band. What we see, then, is hot plasma, at temperatures on the order of 100 million. of degrees. By tracking this hot gas we know how to reconstruct the temperature of the plasma and therefore the potential hole of the cluster – that is, how deep it is. And therefore its mass ».
What mass can a cluster reach?
“Let’s say that if we identified clusters larger than two million billion solar masses we would have problems. Our theories do not contemplate the formation of clusters of any size. Considering the mass and the time available – cosmic time, I mean – for the evolution of these structures, we cannot get to clusters larger than two million billion solar masses. The largest in our sample reach one million and six hundred billion, one million and eight hundred billion… In short, we have clusters that are close to the border ».
Let’s come to your project, Chex-Mate. You have chosen 118 of clusters. Why exactly those?
“We made the selection using data collected by the Planck Space Telescope, in particular the catalogs of objects selected for their Sunyaev-Zel’dovich signal. This is an effect due to the motion of the photons of the Cmb in a gravitational field with high energy electrons, such as that of clusters. The stronger this signal, the more the electrons have energy and the cluster has a high expected mass. Selecting a sample through this effect is almost like making a selection on the mass, so what we get is a representative sample not of the showy properties but of the intrinsic properties of clusters. On a few thousand clusters present in Planck’s Sunyaev-Zel’dovich signal maps, we selected the 118 with the best signal-to-noise ratio and which were distributed in cosmic time with an expected mass useful for the study of their “demography”. And for all these clusters we have obtained, thanks to the three million seconds of observation time with Xmm-Netwon assigned to our project, deep and homogeneous X-band exposures ».
That means? Have you observed all 118 of them for the same time?
“No, on the contrary, it’s like with a camera: being objects with different redshift , therefore at different distances, to obtain homogeneous exposures it is necessary to observe each of them for the required time – those further away require longer exposures, with the same mass. – so as to then be able to compare the signals obtained. And this is what we have done in recent years ».
The acronym of your project, Chex-Mate, alludes to the game of chess, and in particular to checkmate. What game are you playing?
“The game concerns a big problem that has remained unresolved, especially after seeing the data obtained from the Planck satellite. Planck’s observations allowed us to measure the cosmic background radiation and, from this, to arrive at very accurate estimates of cosmological parameters – in the order of one hundred: fantastic results. The same estimates can be made from clusters of galaxies. Scientists from the Planck community tried, but found that the mass of the clusters obtained through observations in X accounted for only 60 percent of the total mass, if the results obtained from the cosmic background radiation were to be reproduced. So we said to ourselves: well, let’s select a sample through the Sunyaev-Zel’dovich effect and let’s see in detail – in a homogeneous way,gravitational lensing in optical band – what is the exact contribution of the X-rays to the current mass ».
Is there any reason why it could only be a partial contribution?
«Yes, the underestimation in X could be due to the so-called hydrostatic bias , that is to say the presence of a component of kinetic energy that we cannot trace well. In order for the estimate of the mass through the measurement of the X-radiation to be reliable, all the kinetic energy of the matter falling into the potential well must be transformed into thermal energy. But if the baryons keep falling towards the potential well there is residual motion, and we can’t measure this from X observations – at least not with current instruments, we will need the future Esa Athena space telescope.to succeed. In short, the suspicion is that, through the X measurements, we are underestimating the mass of the clusters. Dedicated observations on a homogeneous sample, such as the one we are doing, will allow us to measure this discrepancy – the difference between the mass measured by observing the X properties and mass, instead, measured through gravitational lensing . Thus giving “checkmate” to the problem of bias in mass estimation. But at the same time we would also like to arrive at a definitive word – before the next generation of instruments for the measurement and characterization of X-rays – on how much we can really know about the plasma that emits X-rays and which contains the bulk of the baryon matter ».
Read on Astronomy & Astrophysics the article “ The Cluster HEritage project with XMM-Newton: Mass Assembly and Thermodynamics at the Endpoint of structure formation. I. Program overview“, By M. Arnaud, S. Ettori, GW Pratt, M. Rossetti, D. Eckert, F. Gastaldello, R. Gavazzi, ST Kay, L. Lovisari, BJ Maughan, E. Pointecouteau, M. Sereno, I. Bartalucci, A. Bonafede, H. Bourdin, R. Cassano, RT Duffy, A. Iqbal, S. Maurogordato, E. Rasia, J. Sayers, F. Andrade-Santos, H. Aussel, DJ Barnes, R. Barrena, S. Borgani, S. Burkutean, N. Clerc, P.-S. Corasaniti, J.-C. Cuillandre, S. De Grandi, M. De Petris, K. Dolag, M. Donahue, A. Ferragamo, M. Gaspari, S. Ghizzardi, M. Gitti, CP Haines, M. Jauzac, M. Johnston-Hollitt, C. Jones, F. Kéruzoré, AMC Le Brun, F. Mayet, P. Mazzotta, J.-B. Melin, S. Molendi, M. Nonino, N. Okabe, S. Paltani, L. Perotto, S. Pires, M. Radovich, J.-A. Rubino-Martin, L. Salvati, A. Saro, B. Sartoris, G. Schellenberger, A. Streblyanska, P. Tarrio, P. Tozzi, K. Umetsu, RFJ van der Burg, F. Vazza, T.
Featured image: Stefano Ettori, astrophysicist at Inaf Oas in Bologna and principal investigator of the Chex-Mate project
A team of evolutionary biologists from the University of Toronto has shown that Anolis lizards, or anoles, are able to breathe underwater with the aid of a bubble clinging to their snouts.
Anoles are a diverse group of lizards found throughout the tropical Americas. Some anoles are stream specialists, and these semi-aquatic species frequently dive underwater to avoid predators, where they can remain submerged for as long as 18 minutes.
“We found that semi-aquatic anoles exhale air into a bubble that clings to their skin,” says Chris Boccia, a recent Master of Science graduate from the Faculty of Arts & Science’s Department of Ecology & Evolutionary Biology (EEB). Boccia is lead author of a paper describing the finding published this week in Current Biology.
“The lizards then re-inhale the air,” says Boccia, “a maneuver we’ve termed ‘rebreathing’ after the scuba-diving technology.”
The researchers measured the oxygen (O2) content of the air in the bubbles and found that it decreased over time, confirming that rebreathed air is involved in respiration.
Rebreathing likely evolved because the ability to stay submerged longer increases the lizard’s chances of eluding predators.
The authors studied six species of semi-aquatic anoles and found that all possessed the rebreathing trait, despite most species being distantly related. While rebreathing has been studied extensively in aquatic arthropods like water beetles, it was not expected in lizards because of physiological differences between arthropods and vertebrates.
“Rebreathing had never been considered as a potential natural mechanism for underwater respiration in vertebrates,” says Luke Mahler, an assistant professor in EEB and Boccia’s thesis supervisor. “But our work shows that this is possible and that anoles have deployed this strategy repeatedly in species that use aquatic habitats.”
Mahler and co-author Richard Glor, from the University of Kansas, first observed anoles rebreathing in Haiti in 2009 but were unable to carry out further observations or experiments. Another co-author, Lindsey Swierk, from Binghamton University, State University of New York, described the same behaviour in a Costa Rican species in 2019. These early observations suggested that rebreathing was an adaptation for diving, but this idea had not been tested until now.
Boccia became interested in aquatic anoles after encountering one in Panama. He began his rebreathing investigations in Costa Rica in 2017 and continued the research in Colombia and Mexico.
As the authors point out, the rebreathing trait may have developed because anoles’ skin is hydrophobic — it repels water — a characteristic that likely evolved in anoles because it protects them from rain and parasites. Underwater, air bubbles cling to hydrophobic skin and the ability to exploit these bubbles for breathing developed as a result.
While further work is required to understand how the process works in detail, Boccia, Mahler and their co-authors suggest different ways in which rebreathing may function.
In its simplest form, the air bubble on a lizard’s snout likely acts like a scuba tank, providing a submerged animal with a supply of air in addition to the air in its lungs. This is what aquatic arthropods like water beetles do to extend the time they can remain submerged.
The researchers also suggest that the rebreathing process may facilitate using air found in a lizard’s nasal passages, mouth and windpipe that would otherwise not be used by the lizard in breathing.
The bubble may also help rid waste carbon dioxide (CO2) from exhaled air through a process other researchers have already observed in aquatic arthropods. Those studies concluded that because CO2 is highly soluble in water and because the level of CO2 in the bubbles is higher than in the surrounding water, exhaled CO2 dissolves into the surrounding water rather than being rebreathed.
Finally, the authors speculate that the bubble may act as a gill and absorb oxygen from the water — again, something already observed in arthropods. Boccia and Mahler are planning further research to confirm if these rebreathing processes are occurring with anoles.
According to Mahler, “This work enriches our understanding of the creative and unexpected ways that organisms meet the challenges posed by their environments. That is valuable in its own right, but discoveries like this can also be valuable to humans as we seek solutions to our own challenging problems.”
“It’s too early to tell if lizard rebreathing will lead to any particular human innovations,” says Boccia, “But biomimicry of rebreathing may be an interesting proposition for several fields — including scuba-diving rebreathing technology, which motivated our naming of this phenomenon.”
Mahler’s participation in the research was supported by an NSERC Discovery Grant and a Harvard University Ken Miyata Field Research Award. Boccia’s participation was supported by an NSERC CGS M Grant, a National Geographic Young Explorer Grant and a Sigma Xi Grant in Aid of Research.
Reference: Christopher K. Boccia, Lindsey Swierk, Fernando P. Ayala-Varela, “Repeated evolution of underwater rebreathing in diving Anolis lizards”, Current Biology, 2021. DOI: https://doi.org/10.1016/j.cub.2021.04.040
PSI’s Amanda Sickafoose is a coauthor on a paper that discusses Ixion, a large Plutino which is a class of minor bodies located in the 3:2 orbital resonance with Neptune. Ixion was predicted to pass in front of a bright star (Gaia magnitude 10.3) on Oct. 13, 2020. The shadow path, expected to be less than 1,000 kilometers wide, passed over parts of nighttime Arizona and California. Successful observations were made from two telescopes in Arizona.
The occultation itself lasted just under 45 seconds. Ixion is roughly four thousand times fainter than the star it occulted. As shown in the image above, the star was completely visible beforehand and completely blocked out during the occultation. By observing this event, the research team was able to place a lower limit on Ixion’s diameter of 709.6 kilometers (assuming a spherical shape). This size confirms Ixion as being in the top four largest Plutinos and a possible dwarf planet. The work also placed an upper limit of 2 microbars for the pressure of any global atmosphere on Ixion. The lack of atmosphere on Ixion can be compared to Pluto’s tenuous atmosphere of approximately 10 microbars. These are the most accurate measurements of these characteristics for Ixion to date.
Although the goal of the observations was to learn more about Ixion, the star was found to be bigger than expected. Going into and out of the occultation, gradually fading and reappearing starlight was an indication that the star was large with respect to the spatial resolution of the images. Analyses determined that the star’s radius is 130 Solar radii. Only a small number of this type of star, M5 III, has directly measured sizes. Spectral data show that the star is likely a mid-M red giant, which is consistent with the large size.
The publication is led by Stephen Levine of Lowell Observatory and is entitled “Occultation of a Large Star by the Large Plutino (28978) Ixion on 2020 October 13 UTC.” It is available through open access in the Astronomical Journal at https://iopscience.iop.org/article/10.3847/1538-3881/abe76d.
Featured image: Images from the 4.3-meter Lowell Discovery Channel Telescope (LDT) showing the disappearance of the target star during the occultation. (left) The full field of view, with white circles indicating the occultation star (“Occ”), two comparison stars (“Comp A” and “Comp B”), and two sky regions (“Sky 1” and “Sky2”). Each of these regions were used in the data analyses. (right) Zoomed portion of the field taken during the occultation, when Ixion blocked the light from the star. Background stars that are not apparent on the left are visible. The exposure time was only 0.33 seconds; therefore, Ixion itself is too faint to see in this image. (Credit: modified Fig. 3 from Levine et al. 2021)
New findings identify molecular mechanism behind rapid weight gain in patients treated with risperidone
Scientists with UT Southwestern’s Peter O’Donnell Jr. Brain Institute have identified the molecular mechanism that can cause weight gain for those using a common antipsychotic medication. The findings, published in the Journal of Experimental Medicine, suggest new ways to counteract the weight gain, including a drug recently approved to treat genetic obesity, according to the study, which involved collaborations with scientists at UT Dallas and the Korea Advanced Institute of Science and Technology.
“If this effect can be shown in clinical trials, it could give us a way to effectively treat patients for their neuropsychiatric conditions without this serious side effect,” says lead author Chen Liu, Ph.D., assistant professor of internal medicine and neuroscience, and with UTSW’s O’Donnell Brain Institute and Hypothalamic Research Center.
Up to 20 percent of people who take risperidone, an atypical antipsychotic prescribed for a wide variety of neuropsychiatric conditions, add more than 7 percent to their baseline weight within a few weeks of treatment, contributing to other health problems such as high blood cholesterol and type 2 diabetes. The weight gain leads many patients to stop using the medication.
In the study, Liu and his colleagues developed a diet for mice that incorporates the drug and identified changes in gene expression and neuronal activity within the animals’ hypothalamus, a brain region long associated with appetite control. They quickly honed in on a gene called melanocortin 4 (Mc4r), which also is linked to obesity in humans. The Food and Drug Administration recently approved a drug that promotes Mc4r activity to treat some genetic forms of obesity, and Liu and his team showed that giving mice this drug along with risperidone prevented weight gain while maintaining effective treatment in models of schizophrenia – offering hope that this strategy might be effective for human patients as well.
The study was funded by grants from the National Institutes of Health (R01 DK114036, F32DK116427, K01AA024809) and the Korean National Research Foundation (2019R1A2C2005161).
Other researchers who contributed to this study include Li Li, Xiujuan Li, Steven C. Wyler, Xiameng Chen, Rong Wan, Amanda G. Arnold, and Shari G. Birnbaum, all of UTSW; Lin Jia, of UT Dallas; and Eun-Seon Yoo and Jong-Woo Sohn, of Korea Advanced Institute of Science and Technology.
This retrospective study included 904 patients (453 men, 451 women; mean age, 62 years) who underwent lobectomy (n=574) or sublobar resection (n=330) for stage IA non-small cell lung cancer. Two thoracic radiologists independently evaluated findings on preoperative chest CT, later resolving any discrepancies. Recurrences were identified via medical record review.
“In patients with stage IA non-small cell lung cancer, pathologic lymphovascular invasion was observed only in solid-dominant part solid nodules and solid nodules with solid portion diameter over 10 mm,” concluded corresponding author Mi Young Kim from the department of radiology at the University of Ulsan College of Medicine, Asan Medical Center.
“Among such nodules,” the authors of this AJR article continued, “peritumoral interstitial thickening (odds ratio=13.22) and pleural contact (odds ratio=2.45) were independently associated with pathologic lymphovascular invasion.” Moreover, models incorporating these features independently predicted recurrence-free survival after sublobar resection (hazard ratio=5.37–6.05).