Latest news with #UniversityofZürich
Yahoo
20 hours ago
- Science
- Yahoo
What would happen if you tried to land on a gas giant?
Our solar system contains three types of planets. Between the four terrestrial planets–Mercury, Venus, Earth, and Mars–and the distant ice giants of Neptune and Uranus, sit two gas giants: Saturn and Jupiter. These planets are mostly composed of hydrogen and helium gas. Researchers now appreciate that gas planets are more complex than first thought. New findings have implications for our understanding of how these planets formed and will help design future missions to potentially visit them. Gas giants originate from one of two processes. The first method is called core accretion, explains Ravit Helled, a professor of theoretical astrophysics at the University of Zürich. This starts with the birth of a new star, when molecular clouds collapse under gravitational pressure. Whorls of gas–called protoplanetary disks–start to spin around these new stars. Within these gas disks will be heavier particles–dust, rock, or any elements heavier than helium. These particles can clump together and then suck in gas from the surrounding disk, forming a giant planet mainly composed of gas. A second method that may form gas giants called disk instability–this is a newer theory that still causes some controversy among planetary theorists. According to this idea, when massive protoplanetary disks cool down, they become unstable and can produce clumps of rock and gas that evolve into gas giants. Importantly, this proposed formation process happens much more quickly than core accretion. Helled says that Saturn and Jupiter likely formed via core accretion, but that disk instability may 'explain very massive planets at large orbits or giant planets around small mass stars.' Regardless of how they form, the structure of gas giants is nothing like that of terrestrial planets like Earth. Jupiter and Saturn don't have a surface in the same way Earth does. Instead, their atmosphere simply gets thinner until there isn't enough density left to call the surrounding air part of the planet anymore. 'There is no location where you can say, okay, this is where the planet stops,' says Helled. A spaceship attempting to 'land' on Jupiter's 'surface' would have to overcome some significant obstacles. Once you enter the cloud of gas that roughly marks the beginning of a giant like Jupiter, temperature and pressure steadily increase as your head toward the planet's core, and gaseous hydrogen and helium morph into liquid form. While our solar system's gas giants are far from the sun, the core of a gas giant is likely to be incredibly hot–Jupiter's is estimated at around 43,000 degrees Fahrenheit. You'd also have to pass through the thick clouds of ammonia found in Jupiter's upper atmosphere. If you make your ship from tough stuff–tougher than any known substance on Earth–that could survive these conditions, it might make it to a gas giant's core. What it would find there in the alien murk is still unclear. 'For decades, it was assumed that there was a defined core,' says Helled. Recent probe missions, like Juno and Cassini, have orbited Jupiter and Saturn, respectively. The information these probes sent back has changed that view. 'We now think that they have what we call fuzzy or diluted cores,' says Helled. This means that there isn't a clear transition point between the upper layers of liquid gas and liquid hydrogen and helium and the planet's core. In truth, Juno and Cassini's data has revolutionized our understanding of these planet's structures. Helled explains that they likely have complex heat and composition gradients. Jupiter is famously wracked with massive storms, like the Great Red Spot, which produces winds up to 425 mph (640 km/h). Some of these shifts can produce dramatic phenomena. Jupiter and Saturn likely have regions in which helium gas separates from hydrogen. Here, the helium becomes a rain of droplets that pour towards the planet's core. These insights can reveal more about our solar system's giants, as well as similar planets outside our solar system. 'Now we realize that some of the simple assumptions that we've made to model these planets are wrong, and we need to modify the models,' says Helled. This story is part of Popular Science's Ask Us Anything series, where we answer your most outlandish, mind-burning questions, from the ordinary to the off-the-wall. Have something you've always wanted to know? Ask us.
Medscape
13-05-2025
- Health
- Medscape
AI Identifies Novel Predictors of TB in People With HIV
An artificial intelligence (AI) model using routinely collected data predicted subsequent development of active tuberculosis (TB), Swiss researchers reported. The AI model outperformed biological tests for latent TB in identifying HIV-positive patients at high risk of developing TB. As well as immune function and sociodemographic variables, the AI model retained several biomarkers indicative of patients' well-being and metabolism. In Switzerland and other countries with good access to antiretroviral therapy, TB is a rare but serious co-infection in people living with HIV, frequently linked with late HIV diagnosis. To prevent progression to active TB disease, people known to have latent TB infection can be offered preventive treatment with isoniazid and/or rifampicin. But detection of latent TB is challenging, especially in people with HIV. In a previous Swiss analysis, a combined approach using interferon gamma release assays (IGRA) and tuberculin skin tests identified only 30% of people who subsequently developed active TB. 'It was worse than tossing a coin,' Joahnnes Nemeth, MD, an attending physician in the department of infectious diseases and hospital epidemiology at the University of Zürich, Zürich, Switzerland, told Medscape Medical News. The problem is that the tests rely on immune response, which may be impaired. 'You interrogate the very system that is malfunctioning during HIV infection, so it's not a surprise that the tests perform poorly,' he explained. This led him and his colleagues to look into alternative ways to identify patients at risk. They leveraged data from the Swiss HIV Cohort Study, which includes around 70% of people receiving HIV care in the country. Over 23 years' worth of data were analyzed using machine learning, a subset of AI that enables computers to learn patterns from data and make predictions without being explicitly programmed for each task. Their machine learning model employed a random forest — an algorithm which combines the outputs from multiple decision trees. The model looked at data collected at HIV diagnosis in order to predict active TB disease that developed at least 6 months later. Rather than only considering variables which the researchers thought were potential risk factors, the model reviewed all the variables for which they had sufficient data. 'What I really liked about this machine learning approach is that we threw all the data we collect into the machine and just asked it: Can you do something with that?' Nemeth said. 'I think that really paid off.' The first iteration of the model included 48 variables and had a sensitivity of 70.1% and a specificity of 81.0%. A streamlined second version retained 20 variables — making it computationally less demanding — while delivering a sensitivity of 57.1% and specificity of 77.8%. Given that biologic tests had a sensitivity of 30% and specificity of 94%, for Nemeth this 'blows everything of the water.' The model doesn't require additional data collection or have the expense of IGRA. As might be expected, the 20 retained variables included immunological parameters, hematological markers, and sociodemographic factors, but some were more surprising: along with several variables linked with metabolism (cholesterol, high-density lipoprotein, glucose, and creatinine), body mass index, and mean arterial pressure. The researchers noted that TB is associated with malnutrition and said that some of these markers may reflect metabolic perturbations and compromised muscle mass in people at risk for TB. The model was first validated on a portion of the Swiss cohort which it was not trained on, and then on a cohort in Austria. Despite the many parallels between the two cohorts, initially the model performed badly in Austria. The researchers realized the issue stemmed from different migration patterns between the countries: Most people with TB in Switzerland have moved from sub-Saharan Africa, while in Austria, most come from the former Soviet republics. Only after modifying the ethnicity and region of birth variables did the model begin to work effectively. 'This is a cautionary tale,' said Nemeth. 'You go to a very similar setting with a little difference, and all this stops working. With machine learning models, we really have to be careful and test them vigorously before we rely on them.' Emily Wong, MD, is an associate professor at the University of Alabama at Birmingham who has used AI to aid interpretation of chest radiography in South Africa, but was not involved in the new study. The Swiss research 'opens one's eyes to the idea that with very large data sets with lots of clinical variables, you can discern meaningful and predictive patterns that predict whether someone will go on to develop TB,' she told Medscape Medical News. Nemeth is working on an implementation study in which physicians whose patients have never been tested for TB will be randomly allocated to either receive a reminder to test, or a risk score based on the machine learning model. A key question is whether the latter will be enough to convince physicians to take further action, such as offering preventative therapy. Wong noted that the potential benefits and risks (including liver toxicity) of preventative therapy need to be weighed up for each patient. But a machine learning model could help clinicians to do this. 'The idea that in the future, based on key demographic and clinical information of a person, and maybe including their chest x-ray or IGRA test, or maybe not, we would have a well-functioning clinical decision making tool that would guide a health care worker to make TB prevention decisions for the patient in front of them is definitely a worthy goal,' she said. The study was funded by the Swiss National Science Foundation. Nemeth declared receiving honoraria for presentations from Oxford Immunotec and ViiV.
The Guardian
03-04-2025
- Science
- The Guardian
Bonobos may combine words in ways previously thought unique to humans
Bonobos use a combination of calls to encourage peace with their partner during mating rituals, research suggests. The discovery is part of a study that suggests our close evolutionary cousins can string together vocalisations to produce phrases with meanings that go beyond the sum of their parts – something often considered unique to human language. 'Human language is not as unique as we thought,' said Dr Mélissa Berthet, the first author of the research from the University of Zürich. Writing in the journal Science, Berthet and colleagues said that in the human language, words were often combined to produce phrases that either had a meaning that was simply the sum of its parts, or a meaning that was related to, but differed from, those of the constituent words. ''Blond dancer' – it's a person that is both blond and a dancer, you just have to add the meanings. But a 'bad dancer' is not a person that is bad and a dancer,' said Berthet. 'So bad is really modifying the meaning of dancer here.' It was previously thought animals such as birds and chimpanzees were only able to produce the former type of combination, but scientists have found bonobos can create both. The team recorded 700 vocalisations from 30 adult bonobos in the Democratic Republic of the Congo, checking the context of each against a list of 300 possible situations or descriptions. The results reveal bonobos have seven different types of call, used in 19 different combinations. Of these, 15 require further analysis, but four appear to follow the rules of human sentences. Yelps – thought to mean 'let's do that' – followed by grunts – thought to mean 'look at what I am doing', were combined to make 'yelp-grunt', which appeared to mean 'let's do what I'm doing'. The combination, the team said, reflected the sum of its parts and was used by bonobos to encourage others to build their night nests. The other three combinations had a meaning apparently related to, but different from, their constituent calls. For example, the team found a peep – which roughly means 'I would like to …' – followed by a whistle – appeared to mean 'let's stay together' – could be combined to create 'peep-whistle'. This combination was used to smooth over tense social situations, such as during mating or displays of prowess. The team speculated its meaning was akin to 'let's find peace'. The team said the findings in bonobos, together with the previous work in chimps, had implications for the evolution of language in humans, given all three species showed the ability to combine words or vocalisations to create phrases. 'The cognitive building blocks that facilitate this capacity is at least 7m years old,' said Dr Simon Townsend, another author of the research. 'And I think that is a really cool finding.'
