The research, published in Alzheimer’s & Dementia: The Journal of the Alzheimer’s Association, used virtual reality to test the spatial navigation of 100 asymptomatic midlife adults, aged 43-66, from the PREVENT-Dementia prospective cohort study.

Participants had a hereditary or physiological risk of Alzheimer’s disease, due to either a gene (the APOE-ε4 allele) that puts them at risk of the condition, a family history of Alzheimer’s disease, or lifestyle risk factors such as low levels of physical activity. Crucially, these participants were around 25 years younger than their estimated age of dementia onset.

Led by Professor Dennis Chan, the study used a test designed by Dr Andrea Castegnaro and Professor Neil Burgess (all UCL Institute of Cognitive Neuroscience), in which participants were asked to navigate within a virtual environment while wearing VR headsets.

The researchers found that people at greater risk of developing Alzheimer’s disease, regardless of risk factor, were selectively impaired on the VR navigation task, without a corresponding impairment on other cognitive tests. The authors say their findings suggest that impairments in spatial navigation may begin to develop years, or even decades, before the onset of any other symptoms.

First author, Dr Coco Newton (UCL Institute of Cognitive Neuroscience), who carried out the work while at University of Cambridge said: “Our results indicated that this type of navigation behaviour change might represent the very earliest diagnostic signal in the Alzheimer’s disease continuum — when people move from being unimpaired to showing manifestation of the disease.”

The researchers also found that there was a strong gender difference in how participants performed, with the impairment being observed in men and not women.

Dr Newton added: “We are now taking these findings forward to develop a diagnostic clinical decision support tool for the NHS in the coming years, which is a completely new way of approaching diagnostics and will hopefully help people to get a more timely and accurate diagnosis.

“This is particularly important with the emergence of anti-amyloid treatments for Alzheimer’s, which are considered to be most effective in the earliest stages of the disease.

“It also highlights the need for further study of the differing vulnerability of men and women to Alzheimer’s disease and the importance of taking gender into account for both diagnosis and future treatment.”

Professor Chan said: “We are excited by these findings for two main reasons. First, they improve detection of the clinical onset of Alzheimer’s disease, critical for prompt application of treatments.

“Second, the VR navigation test is based on our knowledge of the spatial properties of cells in the brain’s temporal lobe, and the application of cellular neuroscience to clinical populations helps bridge the gap in understanding how disease at the neuronal level can result in the clinical manifestation of disease. This knowledge gap currently represents one of the biggest barriers to progress in Alzheimer’s research.”

The research was carried out in collaboration with the University of Cambridge, jointly funded by the Alzheimer’s Society and an MSD research grant.

Dr Richard Oakley, Associate Director of Research and Innovation at Alzheimer’s Society, said: “One in three people born today will go on to develop dementia, and early and accurate diagnosis of the diseases that cause the condition are vital for people to access the right support, plan for the future, and receive appropriate treatment.

“Very early symptoms of dementia can be subtle and difficult to detect, but problems with navigation are thought to be some of the first changes in Alzheimer’s disease.

“This study was part funded by Alzheimer’s Society and used virtual reality technology showing that a healthy person’s navigation abilities are linked to their dementia risk, based on genetic and environmental factors.

“This innovative technology is a long way from becoming a diagnostic test, but it does provide more evidence about the role of navigational abilities as an early sign of Alzheimer’s disease. More work is needed to develop this technology, but it will be exciting to see how this research may offer a way to spot disease-specific changes early and help people living with dementia in future.”

A fossil skeleton of Perucetus was discovered in Peru and described in a paper in Nature last year. The animal lived about 39 million years ago and belonged to an extinct group of early whales called the basilosaurids.

Perucetus’ bones are unusually dense. Mammal bones usually have a solid exterior and are spongy or hollow in the center. Some animals have more of the center filled in with solid bone, making them dense and heavy. In aquatic animals, heavy bones can offset buoyancy from body fat and blubber, allowing the animal to maintain neutral buoyancy in water or — in the case of the hippopotamus — to walk on river beds.

The fossil whale bones have both extensive in-filling and extra growth of bone on the outside as well, a condition called pachyostosis also seen in some modern aquatic mammals, such as manatees.

Based on a series of assumptions, the original authors (Giovanni Bianucci at the University of Pisa, Italy and colleagues) estimated a body mass for Perucetus of 180 metric tons (ranging from 85 to 340 metric tons). This would make Perucetus as heavy as, or heavier than the biggest blue whales known, even though it is considerably shorter at 17 meters long compared to a blue whale at about 30 meters.

How to weigh a whale?

Professor Ryosuke Motani, a paleobiologist at the UC Davis Department of Earth and Planetary Sciences, said that these estimates would make Perucetus impossibly dense.

“It would have been a job for the whale to stay at the surface, or even to leave the sea bottom — it would have required continuous swimming against the gravity to do anything in the water,” Motani said.

Motani and Nick Pyenson at the Smithsonian Institute National Museum of Natural History reexamined the assumptions used to make those estimates.

The first problem is that Bianucci et al used the fossil bones to estimate the weight of the skeleton, then extrapolated to the weight of the entire animal, assuming that the skeletal and non-skeletal mass would scale at the same rate with increasing body size. But measurements of other animals show this is not the case, Motani and Pyenson argue.

The original estimates also overestimated how much overall body mass increases as a result of pachyostosis. But evidence from manatees shows that their bodies are relatively light relative to their skeletal mass.

Motani and Pyenson estimate that the 17-meter long Perucetus weighed in at 60 to 70 tons, considerably less than the known weights of blue whales. A Perucetus that grew to 20 meters could weigh over 110 tons, still well short of the largest blue whales at 270 tons.

“The new weight allows the whale to come to the surface and stay there while breathing and recovering from a dive, like most whales do,” Motani said.

Paleontologists have not yet uncovered a skull or teeth of Perucetus, so it is hard to tell what it ate. Sustaining a huge body takes a lot of food. Bianucci et al suggested that Perucetus might have browsed on coastal fish and shellfish, or scavenged carcases, as some sharks do. The new slimmed-down size estimate puts Perucetus in a similar range to sperm whales (80 tons, 20 meters long), which hunt large prey such as giant squid.

The massive explosion unleashed a gamma-ray burst, GRB230307A, the second brightest in 50 years of observations and about 1,000 times brighter than a typical gamma-ray burst. GRB230307A was first detected by NASA’s Fermi Gamma-Ray Space Telescope on March 7, 2023.

Using multiple space- and ground-based telescopes, including NASA’s James Webb Space Telescope, the largest and most powerful telescope ever launched into space, scientists were able to pinpoint the source of the gamma-ray burst in the sky and track how its brightness changed.

With the information gathered, the researchers determined the burst was the result of two neutron stars that merged in a galaxy 1 billion light-years from Earth to form a kilonova. The researchers observed evidence of tellurium, one of the rarest elements on Earth.

The breakthrough discovery puts astronomers one step closer to solving the mystery of the origin of elements that are heavier than iron.

“I’m a high energy astrophysicist. I like explosions. I like the gamma rays that come from them. But I’m also an astronomer who really cares about fundamental questions like how did heavy elements form,” Hartmann said.

Gamma-ray bursts (GRBs) are bursts of gamma-ray light — the most energetic form of light — that last anywhere from seconds to minutes. The first GRBs were detected in the 1960s by satellites built to monitor nuclear testing.

GRBs have different causes.

Long duration GRBs are caused by supernovas, the point when a massive star reaches the end of its life and explodes into a burst of light. Short duration GRBs are caused by the merger of two neutron stars, known as a kilonova, or the merger of a neutron star and a black hole.

Although GRB230307A lasted for 200 seconds, scientists saw the afterglow color change from blue to red, a signature of kilonova.

“The burst itself actually indicated a long duration event, and it should have been a normal supernova-type situation. But it had unusual features. It didn’t quite fit the patterns of long bursts,” Hartmann said. “It turns out that this radioactive cloud, that kilonova afterglow, which had all these nuclear synthetic fingerprints in it, is the signature of a binary merger. The excitement comes from using the Webb to identify a chemical fingerprint that we had expected for short bursts and seeing it inside a long burst.”

Hartmann said the Big Bang produced hydrogen and helium. All other elements were made by stars and processes in the interstellar medium.

“Some of them are massive enough to explode and they return that material to their gaseous environments which later make new stars. So, there’s a cycle in the universe that makes us more enriched in carbon, nitrogen, oxygen, all the things we need,” he said. “We call stars the cauldrons of the universe.”

Thermonuclear reactions, or fusion, make stars shine. That leads successively to the production of more heavy elements, Hartmann said. But when it gets to iron, there isn’t much energy left to squeeze out, he said.

So, where do all the heavy elements such as gold and uranium come from?

“The heavy elements have special origins. There are two processes that dominate. One is called rapid; the other is called slow. We believe the r-process happens in those neutron star mergers,” Hartmann said.

Theoretical modeling suggested kilonovas should produce tellurium, but the detection of a spectral line by the James Webb Space Telescope provided experimental evidence. A spectral line is a dark or bright line within a continuous spectrum. It is produced by transitions within atoms or ions.

“We think it’s a pretty secure identification, but it’s not beyond a reasonable doubt like they would say in court,” Hartmann said.

In addition to Hartmann, researchers from several universities in the United States as well as scientists from the Netherlands, the United Kingdom, Italy, Japan, Denmark, Spain, Sweden, Australia, Ireland, France, New Zealand, Canada, Israel, Iceland, Czech Republic and Germany were involved.