A larger power grid has perks, but also has perils that researchers at Northwestern University are hoping to address to expedite integration and improvements to the system.

An obvious challenge in larger grids is that failures can propagate further — in the case of Texas, across state lines. Another is that all power generators need to be kept synchronized to a common frequency in order to transmit energy. The U.S. is served by three “separate” grids: The Eastern interconnection, the Western interconnection and the Texas interconnection, interlinked only by direct-current power lines. Any persistent deviation in frequencies within a region can lead to an outage.

As a result, researchers are searching for ways to stabilize the grid by looking for methods to mitigate deviations in the power generators’ frequencies.

The new Northwestern research shows that counter to assumptions held by some, there are stability benefits to heterogeneity in the power grid. Examining several power grids across the U.S. and Europe, a team led by Northwestern physicist Adilson Motter recently reported that generators operating on different frequencies return to their normal state more quickly when they are damped by “breakers” at different rates than generators around them.

The paper was published March 5 in the journal Nature Communications.

Motter is the Charles E. and Emma H. Morrison Professor in the department of physics and astronomy in the Weinberg College of Arts and Sciences. His research focuses on nonlinear phenomena in complex systems and networks.

Motter compares power grids to a choir: “It’s a little bit like a choir without a conductor. The generators have to listen to others and speak in sync. They react and respond to each other’s frequencies.”

Listen to an out-of-whack frequency, and the result can be a failure. Given the interconnected makeup of the system, a failure can propagate across the network. Historically, these malfunctions have been prevented by using active controllers. However, failures are often caused precisely by control and equipment errors. This points to a need to build additional stability within the design of the system. To achieve that, the team looked into leveraging the natural heterogeneities of the grid.

When the frequencies of the power generators are moved away from the synchronous state, they can swing around for a long time and even become more erratic. To mitigate these fluctuations, they came up with something akin to a door mechanism used to close a door the fastest, but without slamming.

“Mathematically, the problem of damping frequency deviations in a power generator is analogous to the problem of optimally damping a door to get it to close the fastest, which has a known solution in the case of a single door,” Motter said. “But it’s not a single door in this analogy. It’s a network of many doors that are coupled with each other, if you can imagine the doors as power generators.”

When creating an “optimal damping” effect, they discovered that rather than making each damper identical, damping the power generators in a way that is suitably different from each other can further optimize their ability to synchronize to the same frequency as quickly as possible. That is, suitably heterogenous damping across the network can lead to improved stability in the power grids studied by the team.

This discovery could have implications for future grid design as developers work to optimize technology and in considerations to further integrate now separated networks.

The study was supported by Northwestern University’s Finite Earth Initiative (supported by Leslie and Mac McQuown) and ARPA-E Award No. DE-AR0000702 and also benefited from logistical support from the Northwestern Institute for Sustainability and Energy.

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Materials provided by Northwestern University. Original written by Lila Reynolds. Note: Content may be edited for style and length.

Pine Island Glacier is a region of fast-flowing ice draining an area of West Antarctica approximately two thirds the size of the UK. The glacier is a particular cause for concern as it is losing more ice than any other glacier in Antarctica.

Currently, Pine Island Glacier together with its neighbouring Thwaites glacier are responsible for about 10% of the ongoing increase in global sea level.

Scientists have argued for some time that this region of Antarctica could reach a tipping point and undergo an irreversible retreat from which it could not recover. Such a retreat, once started, could lead to the collapse of the entire West Antarctic Ice Sheet, which contains enough ice to raise global sea level by over three metres.

While the general possibility of such a tipping point within ice sheets has been raised before, showing that Pine Island Glacier has the potential to enter unstable retreat is a very different question.

Now, researchers from Northumbria University have shown, for the first time, that this is indeed the case.

Their findings are published in leading journal, The Cryosphere.

Using a state-of-the-art ice flow model developed by Northumbria’s glaciology research group, the team have developed methods that allow tipping points within ice sheets to be identified.

For Pine Island Glacier, their study shows that the glacier has at least three distinct tipping points. The third and final event, triggered by ocean temperatures increasing by 1.2C, leads to an irreversible retreat of the entire glacier.

The researchers say that long-term warming and shoaling trends in Circumpolar Deep Water, in combination with changing wind patterns in the Amundsen Sea, could expose Pine Island Glacier’s ice shelf to warmer waters for longer periods of time, making temperature changes of this magnitude increasingly likely.

The lead author of the study, Dr Sebastian Rosier, is a Vice-Chancellor’s Research Fellow in Northumbria’s Department of Geography and Environmental Sciences. He specialises in the modelling processes controlling ice flow in Antarctica with the goal of understanding how the continent will contribute to future sea level rise.

Dr Rosier is a member of the University’s glaciology research group, led by Professor Hilmar Gudmundsson, which is currently working on a major £4million study to investigate if climate change will drive the Antarctic Ice Sheet towards a tipping point.

Dr Rosier explained: “The potential for this region to cross a tipping point has been raised in the past, but our study is the first to confirm that Pine Island Glacier does indeed cross these critical thresholds.

“Many different computer simulations around the world are attempting to quantify how a changing climate could affect the West Antarctic Ice Sheet but identifying whether a period of retreat in these models is a tipping point is challenging.

“However, it is a crucial question and the methodology we use in this new study makes it much easier to identify potential future tipping points.”

Hilmar Gudmundsson, Professor of Glaciology and Extreme Environments worked with Dr Rosier on the study. He added: “The possibility of Pine Island Glacier entering an unstable retreat has been raised before but this is the first time that this possibility is rigorously established and quantified.

“This is a major forward step in our understanding of the dynamics of this area and I’m thrilled that we have now been able to finally provide firm answers to this important question.

“But the findings of this study also concern me. Should the glacier enter unstable irreversible retreat, the impact on sea level could be measured in metres, and as this study shows, once the retreat starts it might be impossible to halt it.”

The increase in risk was not confined to the elderly and was not uniform across ethnic groups, prompting the researchers to suggest that the long-term burden of covid-19-related illness on hospitals and broader healthcare systems is likely to be substantial.

Although covid-19 is most well known for causing serious respiratory problems, it can affect other organs and systems within the body, including the heart, kidneys, and liver.

Several unexplained symptoms that continue for more than 12 weeks after covid-19 are said to be part of post-covid syndrome (also known as “long covid”), but the long term pattern of organ damage after infection is still unclear.

To investigate this, a team of UK researchers from the Office for National Statistics, University College London and University of Leicester set out to compare rates of organ dysfunction in individuals with covid-19 several months after discharge from hospital with a matched control group from the general population.

Their findings are based on 47,780 individuals (average age 65, 55% men) in hospital in England with covid-19 who were discharged alive by 31 August 2020.

Participants were matched with controls, based on personal characteristics and medical history. Health records were then used to track rates of hospital readmission (or any admission for controls), death from any cause, and diagnoses of respiratory, cardiovascular, metabolic, kidney, and liver diseases until 30 September 2020.

Over an average follow-up of 140 days, nearly a third of individuals who were discharged from hospital after acute covid-19 were readmitted (14,060 of 47,780) and more than 1 in 10 (5,875) died after discharge.

These events occurred at rates of 766 readmissions and 320 deaths per 1,000 person years, which were four and eight times greater, respectively, than those in matched controls.

Rates of respiratory disease, cardiovascular disease, and diabetes were also significantly raised in patients with covid-19, with 539, 66, and 29 new onset diagnoses per 1,000 person years, respectively (equivalent to 27, three, and 1.5 times greater than in matched controls).

Differences in rates of multiorgan dysfunction between patients with covid-19 and matched controls were greater for individuals aged less than 70 than for those aged 70 or older, and in ethnic minority groups compared with the white population, with the largest differences seen for respiratory disease.

Differences in disease rates between men and women were generally small.

This was a large, well-designed study using 10 years of historical clinical records to exactly match individuals with covid-19 to controls. However, the findings are observational, and the authors cannot rule out the possibility that rates of diagnoses in general might have decreased indirectly because of the pandemic, particularly in people not admitted to hospital with covid-19.

“Our findings suggest that the diagnosis, treatment, and prevention of post-covid syndrome requires integrated rather than organ or disease specific approaches,” they write.

And they say urgent research is needed “to understand the risk factors for post-covid syndrome so that treatment can be targeted better to demographically and clinically at risk populations.”

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Materials provided by BMJ. Note: Content may be edited for style and length.

“This is a virus detection and surveillance method that doesn’t require an expensive infrastructure like other approaches,” says Juan Carlos Izpisua Belmonte, co-corresponding author and a professor in Salk’s Gene Expression Laboratory. “We can accomplish with one portable test the same thing that others are using two or three different tests, with different machines, to do.”

Around the world, more than 100 million people have been infected with SARS-CoV-2, the virus that causes COVID-19. A staggering 500,000 Americans have died from COVID-19 to date. Testing the population is key to stopping the spread of the virus. In addition, tracking the spread of new SARS-CoV-2 variants — some of which could respond differently to treatments or vaccines — is critical.

Today, the standard approach to determining whether a nasal swab is positive for COVID-19 is to run a polymerase chain reaction (PCR) test to detect genetic material from the SARS-CoV-2 virus. If the sample is negative, however, patients and clinicians don’t get any information on what might be causing the coronavirus-like symptoms — unless they run separate PCR tests, using different swab samples, for other viruses. And if the sample is positive for SARS-CoV-2, they don’t learn which COVID-19 variant a patient is infected with unless another set of tests is run; those require a large and expensive next-generation gene-sequencing machine.

Last summer, Mo Li, an assistant professor of bioscience at King Abdullah University of Science and Technology in Saudi Arabia, was pondering ways he could lend his expertise in genetic engineering and nanopore sequencing to combatting the COVID-19 pandemic. Li, who previously spent six years as a Salk postdoctoral researcher in the Izpisua Belmonte lab, wondered whether a gene-detection approach called isothermal recombinase polymerase amplification (RPA) coupled with real-time nanopore sequencing might be more useful — and faster, cheaper and more portable — than the current COVID-19 testing approach. He teamed up with Izpisua Belmonte to find out.

Unlike PCR, which cycles through lower and higher temperatures to separate DNA strands and copy them, RPA uses proteins — rather than temperature changes — to accomplish the same thing in only 20 minutes. The technology lets researchers copy longer stretches of DNA, and probe for multiple genes at the same time.

“We quickly realized that we could use this technique to not only detect SARS-CoV-2, but other viruses at the same time,” says Li.

In the new paper, Li and Izpisua Belmonte describe a small, portable device that can screen 96 samples at the same time using the RPA assay. They call the method NIRVANA, for “nanopore sequencing of isothermal rapid viral amplification for near real-time analysis.”

The scientists designed NIRVANA to simultaneously test samples for COVID-19, influenza A, human adenovirus, and non-SARS-CoV-2 human coronavirus. In just 15 minutes, the researchers report, the device begins to report positive and negative results. And within three hours, the device finalizes results on all 96 samples — including the sequences of five regions of SARS-CoV-2 that are particularly prone to accumulate mutations leading to new variants such as the B.1.1.7 variant identified in the UK.

Li and Izpisua Belmonte tested NIRVANA on 10 samples known to be positive for SARS-CoV-2, 60 samples of unknown SARS-CoV-2 status, as well as samples of municipal wastewater harboring the SARS-COV-2 virus and others. In all cases, the assay was able to correctly identify which viruses were present. The sequencing data also allowed them to narrow down the origin of SARS-CoV-2 in positive samples; differentiating strains from China and Europe, for instance.

“The design of this assay is really flexible, so it’s not just limited to the examples we’ve shown,” says Li. “We can easily adapt it to tackle another pathogen, even something new and emergent.”

With the small size and portability of the NIRVANA workflow, it could be used for fast virus detection at schools, airports or ports, the researchers say. It also could be used to monitor wastewater or streams for the presence of new viruses.

“The pandemic has provided two important lessons: first, test widely and quickly, and second, know your variants. Our NIRVANA method provides a promising solution to these two challenges not only for the current pandemic but also for possible future ones,” says Izpisua Belmonte, who holds the Roger Guillemin Chair at Salk. Market analysis would be required to determine whether the initial cost of commercialization — and the constant tweaks to the test needed to make sure it detected new variants or new viruses of interest — are worth it, Belmonte adds.

In addition to Izpisua Belmonte and Li, other authors on the study were Concepcion Rodriguez Esteban of Salk; Chongwei Bi, Gerargo Ramos-Mandujano, Sharis Hala, Jinna Xu, Sara Mfarrej, Yeteng Tian and Arnab Pain of King Abdullah University of Science and Technology (KAUST); Estrella Nunez Delicado of UCAM Universidad Católica San Antonio de Murcia; Fadwa Alofi of King Fahad Hospital; Asim Khogeer of Saudi Arabia’s Ministry of Health; Anwar Hashem of King Abdulaziz University; and Naif Almontashiri of Taibah University.

The work described in the current paper was supported by a competitive research grant from the King Abdullah University of Science and Technology.