With these and other emerging applications in mind, MIT researchers demonstrated a new millimeter-wave multiple-input-multiple-output (MIMO) wireless receiver architecture that can handle stronger spatial interference than previous designs. MIMO systems have multiple antennas, enabling them to transmit and receive signals from different directions. Their wireless receiver senses and blocks spatial interference at the earliest opportunity, before unwanted signals have been amplified, which improves performance.

Key to this MIMO receiver architecture is a special circuit that can target and cancel out unwanted signals, known as a nonreciprocal phase shifter. By making a novel phase shifter structure that is reconfigurable, low-power, and compact, the researchers show how it can be used to cancel out interference earlier in the receiver chain.

Their receiver can block up to four times more interference than some similar devices. In addition, the interference-blocking components can be switched on and off as needed to conserve energy.

In a mobile phone, such a receiver could help mitigate signal quality issues that can lead to slow and choppy Zoom calling or video streaming.

“There is already a lot of utilization happening in the frequency ranges we are trying to use for new 5G and 6G systems. So, anything new we are trying to add should already have these interference-mitigation systems installed. Here, we’ve shown that using a nonreciprocal phase shifter in this new architecture gives us better performance. This is quite significant, especially since we are using the same integrated platform as everyone else,” says Negar Reiskarimian, the X-Window Consortium Career Development Assistant Professor in the Department of Electrical Engineering and Computer Science (EECS), a member of the Microsystems Technology Laboratories and Research Laboratory of Electronics (RLE), and the senior author of a paper on this receiver.

Reiskarimian wrote the paper with EECS graduate students Shahabeddin Mohin, who is the lead author, Soroush Araei, and Mohammad Barzgari, an RLE postdoc. The work was recently presented at the IEEE Radio Frequency Circuits Symposium and received the Best Student Paper Award.

Blocking interference

Digital MIMO systems have an analog and a digital portion. The analog portion uses antennas to receive signals, which are amplified, down-converted, and passed through an analog-to-digital converter before being processed in the digital domain of the device. In this case, digital beamforming is required to retrieve the desired signal.

But if a strong, interfering signal coming from a different direction hits the receiver at the same time as a desired signal, it can saturate the amplifier so the desired signal is drowned out. Digital MIMOs can filter out unwanted signals, but this filtering occurs later in the receiver chain. If the interference is amplified along with the desired signal, it is more difficult to filter out later.

“The output of the initial low-noise amplifier is the first place you can do this filtering with minimal penalty, so that is exactly what we are doing with our approach,” Reiskarimian says.

The researchers built and installed four nonreciprocal phase shifters immediately at the output of the first amplifier in each receiver chain, all connected to the same node. These phase shifters can pass signal in both directions and sense the angle of an incoming interfering signal. The devices can adjust their phase until they cancel out the interference.

The phase of these devices can be precisely tuned, so they can sense and cancel an unwanted signal before it passes to the rest of the receiver, blocking interference before it affects any other parts of the receiver. In addition, the phase shifters can follow signals to continue blocking interference if it changes location.

“If you start getting disconnected or your signal quality goes down, you can turn this on and mitigate that interference on the fly. Because ours is a parallel approach, you can turn it on and off with minimal effect on the performance of the receiver itself,” Reiskarimian adds.

A compact device

In addition to making their novel phase shifter architecture tunable, the researchers designed them to use less space on the chip and consume less power than typical nonreciprocal phase shifters.

Once the researchers had done the analysis to show their idea would work, their biggest challenge was translating the theory into a circuit that achieved their performance goals. At the same time, the receiver had to meet strict size restrictions and a tight power budget, or it wouldn’t be useful in real-world devices.

In the end, the team demonstrated a compact MIMO architecture on a 3.2-square-millimeter chip that could block signals which were up to four times stronger than what other devices could handle. Simpler than typical designs, their phase shifter architecture is also more energy efficient.

Moving forward, the researchers want to scale up their device to larger systems, as well as enable it to perform in the new frequency ranges utilized by 6G wireless devices. These frequency ranges are prone to powerful interference from satellites. In addition, they would like to adapt nonreciprocal phase shifters to other applications.

This research was supported, in part, by the MIT Center for Integrated Circuits and Systems.

This study, co-led by Dr Skye Yunshu TIAN from the University of Bonn, who conducted the major part of the research at The University of Hong Kong (HKU), along with Professor Moriaki YASUHARA from HKU School of Biological Sciences, the Swire Institute of Marine Science (SWIMS) and Institute for Climate and Carbon Neutrality (ICCN), as well as Dr Fabien L. CONDAMINE of Centre National de la Recherche Scientifique (CNRS), has now been published in the journal Nature.

The researchers began their investigation by examining sediment samples from the Indo-Australian Archipelago in the laboratory and identifying the fossils they contained. “We wanted to understand how the marine biodiversity of the Indo-Australian Archipelago evolved and persisted, and what factors were responsible for the disproportionately high diversity in the tropics,” said first author Skye Tian.

Their findings revealed that the archipelago had shown an increase in diversification since the early Miocene, around 20 million years ago. Approximately 2.6 million years ago, the number of species approached a plateau. Interestingly, there were no major extinction events during the entire study period. “The increase in diversity was primarily driven by the habitat factor, as tectonic collisions (movements of Earth’s plates) in Southeast Asia created extensive areas of shallow marine habitats,” Skye noted.

Around 14 million years ago, the region’s thermal stress, or excessive heat, began to moderate. “This moderation was crucial for the development of the hotspot,” Skye continued. “During the Eocene (56 to 34 million years ago), excessively high tropical temperatures in warm climate zones hindered the increase in diversity. The cooling after that allowed for a more favourable environment for biodiversity to flourish.” However, this rich biodiversity could be at risk. “Our palaeobiological results suggest that we could quickly lose the fantastic diversity of the tropical hotspot if the ongoing anthropogenic warming intensifies.” Skye added.

Professor Moriaki Yasuhara further elaborated: “This reconstruction of the long-term history of the Coral Triangle diversity hotspot enables us to better understand how diversity hotspot moved from ‘Tethys (ancient Mediterranian region)’ region to the present place of the Coral Triangle and developed there. These are what we didn’t know too clearly before. And also our results tells us why Coral Triangle diversity is much higher than that of the Caribbean Sea, that is probably because the Coral Triangle didn’t experience large extinction event by luck.”

To date, many investigations in the field have established intuitive links that are less direct than that: Air pollution exposure while young is consistently associated with lung problems during childhood — and childhood lung problems are consistently associated with lung issues as an adult.

The current study, published in the American Journal of Respiratory and Clinical Care Medicine, is one of only a few to show the direct connection between childhood air pollution exposure and adult lung health, a connection not fully explained by air pollution impacts on lung health during childhood. It opens the possibility of yet-to-be-understood factors explaining the path from early air pollution exposure to respiratory maladies many years later.

The team drew upon the USC Children’s Health Study, a large-scale, decades-long study following cohorts of Southern Californians starting at school-age and, for many participants, continuing into adulthood. Importantly, the link between childhood air pollution exposure and adult bronchitis symptoms persisted even when the researchers adjusted for asthma or bronchitis symptoms early in life — a finding that came as a surprise.

“We would expect that these observable impacts on childhood respiratory health would explain the relationship between childhood air pollution exposure and adult respiratory health,” said corresponding author Erika Garcia, PhD, MPH, assistant professor of population and public health sciences at the Keck School of Medicine. “Our results suggest that childhood air pollution exposure has more subtle effects on our respiratory system that still impact us in adulthood.”

Safeguarding lung health, now and later

The focus on exposure during youth is motivated in part by the fact that children are particularly vulnerable to the effects of air pollution. Their respiratory and immune systems are still developing and compared to adults, they breathe in more air relative to their body mass.

Ultimately the concern is twofold, for the health of young people today and for their future health when they grow up. Notably, among study participants with recent bronchitis symptoms as adults, average childhood exposure to a pollutant called nitrogen dioxide fell far below annual Environmental Protection Agency standards — just a bit over half the limit that was set in 1971 and remains in place today.

“This study highlights the importance of lowering air pollution, and especially exposure during the critical period of childhood,” Garcia said. “Because there’s only so much that we can do as individuals to control our exposure, the need to protect children from the adverse effects of air pollution is better addressed at the policy level.”

The study population comprised 1,308 Children’s Health Study participants with an average age of 32 at their adult assessment. The researchers asked about recent bouts of bronchitis symptoms — having either bronchitis, chronic cough, or congestion or phlegm production not associated with a cold. One-quarter of participants had experienced bronchitis symptoms within the previous 12 months.

Presence of bronchitis symptoms was associated with exposure between birth and age 17 to two types of pollutants. One type groups together tiny particles in the air such as dust, pollen, ash from wildfires, industrial emissions and products from vehicle exhaust. The other, nitrogen dioxide, is a byproduct of combustion in automobiles, planes, boats and power plants that is known to hurt lung function.

Long-running health research proves vital to igniting discovery

For as comprehensive an analysis as possible, average pollutant exposure over childhood was based on month-by-month estimates. The researchers matched up family home address at each time point with contemporaneous local air quality measurements taken by the EPA and through the Children’s Health Study.

“We’re fortunate to have this fantastic and nuanced longitudinal study,” Garcia said. “We can learn a lot about how earlier experiences impact adult health. That’s thanks to a long-term team effort from the participants themselves, their families, the schools they attended and all the research staff and investigators who conducted interviews and generated and analyzed data over the years.”

The current study included additional analyses to rule out factors such as prenatal exposure to nitrogen dioxide, current air pollution exposure as adults and the effects of socioeconomic status in childhood or adulthood as drivers of bronchitis symptoms in adults.

Pollution exposure in youth may hurt lung health for some more than others

Garcia and her colleagues also found that the effect of nitrogen dioxide and particulate matter exposure during childhood on bronchitis symptoms among adults was stronger for those who had been diagnosed with asthma as kids.

“There may be a subpopulation that is more sensitive to the effects of air pollution,” Garcia said. “We may want to be especially careful to protect them from exposure, so we can improve their outcomes later in life. Reducing air pollution would have benefits not only for current asthma in children but also for their respiratory health as they grow into adulthood.”

She and her colleagues are following up to examine how the level of air pollution exposure at different ages during youth influences breathing issues as an adult. Other future research directions building on the current study’s results could include looking into other markers of childhood and adult respiratory health, such as how well asthma was controlled, or exploring a potential genetic component.

About this study

The study’s co-authors are Zoe Birnhak, Scott West, Steve Howland, Rob McConnell, Shohreh. Farzan, Theresa Bastain, Rima Habre and Carrie Breton, all of the Keck School of Medicine; and Frederick Lurmann and Nathan Pavlovic of the environmental consulting firm Sonoma Technology.

This research received support from the National Institutes of Health (UH3OD023287, P30ES007048).

IIASA researchers adopted a waste systems perspective to identify hotspots of land-waste leakage, and determined which rivers, lakes, and coastal areas are particularly at risk. The results indicate a need for urgent action.

“Our study shows that the majority of leakage of municipal solid waste — everyday items that are discarded by people — into aquatic environments occur in Africa, China, India, and South Asia. It’s necessary to start focusing on improving waste management systems in these affected areas,” explains study lead author Adriana Gomez Sanabria, a researcher in the Pollution Management Research Group of the IIASA Energy, Climate, and Environment Program.

The study highlights that focusing on single waste streams can lead to unintended consequences. For example, as single-use plastic cups are replaced with paper cups, the amount of paper waste has increased. Therefore, it is crucial to set targets that address multiple waste streams simultaneously. Additionally, the study emphasizes the importance of universal waste collection as the primary strategy to prevent waste leakage into terrestrial and aquatic environments, even in a scenario where overall waste generation is reduced.

“Our analysis shows that there is a pressing need to establish a standardized framework to monitor waste generation, composition, and flows. This framework should help us track the effectiveness of actions, including political, economic, and technological measures aimed at reducing waste and improving waste management systems,” notes Florian Lindl, a study coauthor and researcher in the IIASA Pollution Management Research Group.

The research team notes that their study addresses a crucial gap in our understanding of how waste management systems play an important role in addressing various environmental impacts. By examining the interaction between waste management and waste leakage, effective strategies can be identified to reduce pollution in aquatic environments and preserve ecosystems. This knowledge is vital for shaping policies and promoting sustainable development practices that minimize the environmental footprint of our consumption habits.

“We need to understand that the primary function of waste management systems is to protect human health and the environment. As creators of the waste crisis, we must take responsibility by changing our behavior to reduce consumption through refuse, rethink, and reuse practices,” concludes Gomez Sanabria.

The Texas law prohibiting abortions after a fetal heartbeat could be detected — as early as five or six weeks — went into effect September 1, 2021. At the time, the law — Senate Bill 8, or S.B. 8 — was the most stringent state abortion law in the country. It did not allow exemptions for congenital anomalies.

The researchers’ analysis of monthly death certificate data in Texas and the rest of the United States found that between 2021 and 2022, infant deaths in Texas rose from 1,985 to 2,240, a year-over-year increase of 255 deaths. This corresponds to a 12.9 percent increase in infant deaths in Texas versus a 1.8 percent increase in infant deaths in the rest of the U.S. during the same period. The study defines infants as under 12 months old.

The study was published online June 24 in JAMA Pediatrics.

The findings come as more U.S. states enact stricter abortion laws following the U.S. Supreme Court’s 2022 Dobbs decision, the landmark ruling that overturned Roe v. Wade and returned abortion policymaking to the states.

To approximate the causal impact of S.B. 8, the authors narrowed their analysis to examine changes in the expected number of infant deaths in Texas from March to December 2022 — the time period that captures the first set of pregnancies under S.B. 8. The researchers estimate there were 216 excess infant deaths in Texas that would most likely not have occurred from March to December 2022 had the state’s abortion law not been in place. This is equivalent to a 12.7 percent increase above the expected 1,697 infant deaths for this time period. There were 1,913 observed deaths in Texas from March to December 2022.

An analysis of neonatal deaths — deaths in the first 28 days — found similar patterns, with an estimated 145 excess deaths in the post-policy period. These results were not observed in other states.

The new study is thought to be the first to examine how the Texas abortion ban may have impacted infant deaths in the state and is among the first to present evidence evaluating recent abortion bans and pre-viability restrictions. Prior research has shown that states with more abortion restrictions see more infant deaths than those without. The authors note that these earlier studies evaluate fundamentally different and less severe abortion restrictions and primarily examine correlation.

“Our study is particularly relevant given the June 2022 Dobbs Supreme Court decision that returned abortion lawmaking to states and subsequent rollbacks of reproductive rights in many states,” says Alison Gemmill, PhD, assistant professor in the Bloomberg School’s Department of Population, Family and Reproductive Health and one of the study’s lead authors. “These findings suggest that restrictive abortion policies may have important unintended consequences in terms of infant health and the associated trauma to families and medical costs.”

For their month-by-month causal analysis, the researchers drew from infant death certificates in Texas and 28 comparison states from 2018 through 2022. They excluded the District of Columbia and several states that had fewer than 10 infant deaths in any month from 2018 to 2022, as the exact counts are not provided in currently publicly available data. The researchers selected March 2022 as the first cohort exposed to the Texas abortion policy because these infants, if born full term, would have been approximately 10 to 14 weeks gestation when the Texas law went into effect in September 2021. Before S.B. 8’s enactment, people would have been able to seek termination in the event a fetal issue was detected during screening prior to 20 weeks gestation.

In an analysis of cause of death using all 2021 and 2022 death certificate data, the researchers found that Texas had atypical increases in infant deaths due to congenital anomalies, the leading cause of infant death. Infant deaths attributable to congenital anomalies increased 22.9 percent in Texas between 2021 and 2022 versus a decrease of 3.1 percent in the rest of the U.S. during the same period. Another divergent cause of death pattern in Texas was infant deaths from accidents, which increased by 21 percent in Texas versus a one percent increase in the rest of the U.S.

“Our results suggest that restrictive abortion policies that limit pregnant people’s ability to terminate pregnancies, particularly those with fetal abnormalities diagnosed later in pregnancy, may lead to increases in infant mortality,” says Suzanne Bell, PhD, MPH, assistant professor in the Bloomberg School’s Department of Population, Family and Reproductive Health and one of the study’s lead authors. “These findings make clear the potentially devastating consequences abortion bans can have on pregnant people and families who are unable to overcome barriers to this essential reproductive health service.”

The authors note that the data did not include maternal and clinical characteristics of infant deaths, thus limiting the authors’ ability to explore potential mechanisms behind these findings.

The researchers are currently studying the impact across socioeconomic groups that abortion bans have on live births and infant mortality in Texas and other states that banned abortion following Dobbs.

This study was supported by the Hopkins Population Center from the National Institute of Child Health and Human Development (P2CHD042854).

Exoplanets are abundant in our galaxy. The most common are those between the radius of the Earth (around 6,400 km) and Neptune (around 25,000 km), known as ”sub-Neptunes”. It is estimated that 30% to 50% of sun-like stars contain at least one of these.

Calculating the density of these planets is a scientific challenge. To estimate their density, we must first measure their mass and radius. Problem: planets whose mass is measured by the TTV (Transit-Timing Variation) method are less dense than planets whose mass has been measured by the radial velocity method, the other possible measurement method.

”The TTV method involves measuring variations in transit timing. Gravitational interactions between planets in the same system will slightly modify the moment at which the planets pass in front of their star,” explains Jean-Baptiste Delisle, scientific collaborator in the Astronomy Department of the UNIGE Faculty of Science and co-author of the study. ”The radial velocity method, on the other hand, involves measuring the variations in the star’s velocity induced by the presence of the planet around it”.

Eliminating any bias

An international team led by scientists from NCCR PlanetS, UNIGE and UNIBE has published a study explaining this phenomenon. It is due not to selection or observational biases, but to physical reasons. ”The majority of systems measured by the TTV method are in resonance,” explains Adrien Leleu, assistant professor in the Astronomy Department of the UNIGE Faculty of Science and principal author of the study.

Two planets are in resonance when the ratio between their orbital periods is a rational number. For example, when a planet makes two orbits around its star, another planet makes exactly one. If several planets are in resonance, it forms a chain of Laplace resonances. ”We therefore wondered whether there was an intrinsic connection between density and the resonant orbital configuration of a planetary system,” continues the researcher.

To establish the link between density and resonance, astronomers first had to rule out any bias in the data by rigorously selecting planetary systems for statistical analysis. For example, a large, low-mass planet detected in transit requires more time to be detected in radial velocities. This increases the risk of observations being interrupted before the planet is visible in the radial velocity data, and therefore before its mass is estimated.

”This selection process would lead to a bias in the literature in favor of higher masses and densities for planets characterized with the radial velocity method. As we have no measurement of their masses, the less dense planets would be excluded from our analyses,” explains Adrien Leleu.

Once this data cleaning had been carried out, the astronomers were able to determine, using statistical tests, that the density of sub-Neptunes is lower in resonant systems than their counterparts in non-resonant systems, regardless of the method used to determine their mass.

A question of resonance

The scientists suggest several possible explanations for this link, including the processes involved in the formation of planetary systems. The study’s main hypothesis is that all planetary systems converge towards a resonance chain state in the first few moments of their existence, but only 5% remain stable. The other 95% become unstable. The resonance chain then breaks down, generating a series of ”catastrophes”, such as collisions between planets. The planets fuse together, increasing their density and then stabilizing in non-resonant orbits.

This process generates two very distinct populations of Sub-Neptunes: dense and less dense. ”The numerical models of planetary system formation and evolution that we have developed at Bern over the last two decades reproduce exactly this trend: planets in resonance are less dense. This study, moreover, confirms that most planetary systems have been the site of giant collisions, similar or even more violent than the one that gave rise to our Moon,” concludes Yann Alibert, professor at UNIBE’s Space Research and Planetary Sciences Division (WP) and co-director of the Center for Space and Habitability and co-author of the study.

Researchers led by the University of Cambridge used artificial intelligence techniques to map slush on Antarctic ice shelves, and found that 57% of all meltwater is held in the form of slush, with the remaining amount in surface ponds and lakes.

As the climate warms, more meltwater is formed on the surface of ice shelves, the floating ice surrounding Antarctica which acts as a buttress against glacier ice from inland. Increased meltwater can lead to ice shelf instability or collapse, which in turn leads to sea level rise.

The researchers also found that slush and pooled meltwater leads to 2.8 times more meltwater formation than predicted by standard climate models, since it absorbs more heat from the sun than ice or snow. The results, reported in the journal Nature Geoscience, could have profound implications for ice shelf stability and sea level rise.

Each summer as the weather warms, water pools on the surfaces of Antarctica’s floating ice shelves. Previous research has shown that surface meltwater lakes can contribute to ice shelf fracture and collapse, as the weight of the water can cause the ice to bend or break. However, the role of slush in ice shelf stability is more difficult to determine.

“We can use satellite imagery to map meltwater lakes across much of Antarctica, but it’s hard to map slush, because it looks like other things, such as shadows from clouds, when viewed from a satellite,” said lead author Dr Rebecca Dell from Cambridge’s Scott Polar Research Institute (SPRI). “But using machine learning techniques, we can go beyond what the human eye can see and get a clearer picture of how slush might be affecting ice in Antarctica.”

Using optical data from NASA’s Landsat 8 satellite, the Cambridge researchers, working with researchers from the University of Colorado Boulder and the Delft University of Technology, trained a machine learning model to obtain monthly records of slush and meltwater lakes across 57 Antarctic ice shelves between 2013 and 2021.

“Machine learning allows us to use more information from the satellite, since it can work with more wavelengths of light than the human eye can see,” said Dell. “This allows us to determine what is and isn’t slush, and then we can train the machine learning model to quickly identify it across the whole continent.”

“We’re interested in learning how much slush is present during the Antarctic summer, and how it’s changed over time,” said co-author Professor Ian Willis, also from SPRI.

Using their machine learning model, the researchers found that in the peak of the Antarctic summer in January, over half (57%) of all meltwater on Antarctica’s ice shelves is held in slush, with the remaining 43% in meltwater lakes.

“This slush has never been mapped on a large scale across all of Antarctica’s large ice shelves, so over half of all surface meltwater has been ignored until now,” said Dell. “This is potentially significant for the hydrofracture process, where the weight of meltwater can create or enlarge fractures in the ice.”

Meltwater affects the stability of the floating ice shelves that fringe the Antarctic coastline. As the climate warms and melt rates in Antarctica increase, meltwater — whether in the form of lakes or slush — can get into cracks on the ice, causing the cracks to get bigger. This can cause fractures in the ice shelf, and could cause vulnerable ice shelves to collapse, which in turn would allow inland glacier ice to spill into the ocean and contribute to sea level rise.

“Since slush is more solid than meltwater, it won’t cause hydrofracture in the same way that water from a lake does, but it’s definitely something we need to consider when attempting to predict how or whether ice shelves will collapse,” said Willis.

In addition to the potential implications of slush on hydrofracture, it also has a large effect on melt rates. Since slush and lakes are less white than snow or ice, they absorb more heat from the sun, causing more snowmelt. This extra melt is currently unaccounted for in climate models, which may lead to underestimates in projections of ice sheet melting and ice shelf stability.

“I was surprised that this meltwater was so poorly accounted for in climate models,” said Dell. “Our job as scientists is to reduce uncertainty, so we always want to improve our models so they are as accurate as possible.”

“In future, it’s likely that places in Antarctica that currently don’t have any water or slush will start to change,” said Willis. “As the climate continues to warm, more melting will occur, which could have implications for ice stability and sea level rise.”

The research was supported in part by the European Space Agency and the Natural Environment Research Council (NERC), part of UK Research and Innovation (UKRI). Rebecca Dell is a Fellow of Trinity Hall, Cambridge.