How ions flow like a liquid through a solid crystal

Researchers in Japan used a simple physical model and revealed a fundamental connection between sublattice melting and cooperative ion transport

The University of Osaka

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image: 

Basic structure of the superionic conductor identified in this study: Host particles form a stable crystalline framework through strong steric repulsion. Carrier particles, on the other hand, exist at low density in the interstitial spaces between the host particles. Owing to weak long-range interactions (dashed lines), they form a crystalline structure at low temperatures. As the temperature increases, however, we found that the carrier particles melt prior to the host particles while the host crystalline framework remains intact; this process is known as sublattice melting.

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Credit: Takeshi Kawasaki

Osaka, Japan - A research team led by the University of Osaka, working with The National Institute of Advanced Industrial Science and Technology (AIST), RIKEN, and the Institute of Science Tokyo has uncovered a fundamental mechanism behind superionic conduction, in which ions move rapidly through a solid while its crystalline framework remains intact. Using a simple physical model, the researchers connected “sublattice melting” with cooperative and spatially heterogeneous ion transport. The findings offer a unified explanation for superionic conduction and could help guide the design of next-generation solid-state batteries.

Superionic conductors are solid materials in which certain ions move almost as freely as they do in a liquid, making them attractive for solid-state batteries. They have traditionally been studied on a material-by-material basis since real materials often possess complex crystal structures and chemical compositions. This has made it difficult to identify the essential physical mechanism underlying superionic conduction, independent of any single material’s chemistry.

The team constructed a chemically neutral model containing a rigid lattice of host particles and smaller mobile carrier particles. It retained only the interactions considered essential for superionic conduction: strong, short-range repulsion that stabilizes the host framework and softer, longer-range interactions between carriers.

As the temperature increased, the carriers lost their ordered arrangement and began moving like a liquid while the host lattice remained crystalline. This selective loss of order is known as sublattice melting. Near the transition, carriers did not simply hop independently between fixed sites. Instead, they moved cooperatively in spatially heterogeneous, string-like patterns.

The researchers also found that increasingly anharmonic or non-spring-like lattice vibrations softened the carriers’ local environment and promoted collective motion. Adjusting particle density shifted the onset of sublattice melting, while simulations using a three-dimensional model of silver iodide reproduced similar transport regimes.

Because the model captures the essential physics without relying on any specific chemistry, its conclusions apply broadly across many materials. The findings are expected to provide design principles for next-generation solid-state battery and energy-conversion materials with high ionic conductivity, contributing to more efficient materials development.

“Superionic conduction has long been difficult to understand because of the complexity of real materials,” says senior author Takeshi Kawasaki. “By deliberately starting from a simple model, we identified broadly applicable physics that could guide the design of new ion-conducting materials.”

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The article, “Probing Anharmonic and Heterogeneous Carrier Dynamics Across Sublattice Melting in a Minimal Model Superionic Conductor

,” was published in Proceedings of the National Academy of Sciences of the United States of America at DOI: https://doi.org/10.1073/pnas.2605867123

 

About The University of Osaka

The University of Osaka was founded in 1931 as one of the seven imperial universities of Japan and is now one of Japan's leading comprehensive universities with a broad disciplinary spectrum. This strength is coupled with a singular drive for innovation that extends throughout the scientific process, from fundamental research to the creation of applied technology with positive economic impacts. Its commitment to innovation has been recognized in Japan and around the world. Now, The University of Osaka is leveraging its role as a Designated National University Corporation selected by the Ministry of Education, Culture, Sports, Science and Technology to contribute to innovation for human welfare, sustainable development of society, and social transformation.

Website: https://resou.osaka-u.ac.jp/en

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Journal

Proceedings of the National Academy of Sciences

DOI

10.1073/pnas.2605867123 

Method of Research

Computational simulation/modeling

Subject of Research

Not applicable

Article Title

Probing Anharmonic and Heterogeneous Carrier Dynamics Across Sublattice Melting in a Minimal Model Superionic Conductor

Article Publication Date

17-Jul-2026

The trajectories of carrier particles in the superionic conducting regime in our model: The colors of the trajectory distinguish individual particles. The carrier particles move in a liquid-like manner through the interstitial spaces between the host particles forming the crystalline framework, clearly demonstrating their rapid transport.

Credit

Takeshi Kawasaki

New ammonia post-injection strategy cuts engine NOx emissions by 14.4%

Shanghai Jiao Tong University Journal Center

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Schematic diagram of the experiment system

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Credit: Rui Yang, Zining Yu, Jianan Li, Zongyu Yue, Hu Wang, Leilei Xu, Xue-Song Bai & Mingfa Yao.

Researchers from Tianjin University and Lund University have developed a pioneering in-cylinder active reduction strategy to combat the high NOx emissions that have long hindered the adoption of ammonia-fueled internal combustion engines (ICEs). By utilizing an ammonia post-injection (API) technique, the research team successfully reduced NOx emissions by 14.4% without compromising combustion efficiency. 

Ammonia is widely recognized as a promising carbon-free fuel for the transportation and energy sectors. However, its fuel-bound nitrogen content leads to significant NOx emissions during combustion, posing a major challenge for meeting increasingly stringent environmental regulations, such as the Euro 7 standard. 

In the study published in ENGINEERING Energy, the researchers demonstrated that ammonia can serve a dual purpose: as a fuel and as an agent for Selective Non-Catalytic Reduction (SNCR)—a chemical process that breaks down NOx into harmless nitrogen. 

Key Research Highlights:

• Innovative NOx Control: The study reveals the NOx evolution and reduction mechanisms induced by ammonia post-injection, providing a robust theoretical and experimental basis for in-cylinder emission control. 
• Mechanistic Insights: Detailed chemical kinetics analysis identifies that NH2 radicals play the overwhelmingly dominant role in reducing both NO and NO2 within the combustion chamber. 
• Effective Emission Reduction: Engine experiments confirmed that by appropriately delaying the post-injection timing, a 14.4% reduction in NOx emissions was achieved while maintaining high combustion efficiency. 
• Reaction Pathways: The study elucidates the SNCR reaction pathways, showing that NO is primarily reduced to N2 via three distinct pathways involving NH and NH2 radicals. 

The researchers utilized a high-precision Computational Fluid Dynamics (CFD) model to visualize the combustion process. Their simulations showed that post-injected ammonia efficiently reacts with existing NOx in the cylinder. While the strategy effectively cuts NOx, the team also observed trade-offs, including increased N2O (a potent greenhouse gas) and unburned NH3 emissions when the post-injection timing was excessively delayed. 

"This study provides an innovative method for reducing NOx emissions from ammonia combustion," the authors noted. "Combined with the inherent low NOx emission characteristics of ammonia diffusion combustion, this approach holds great promise for achieving effective NOx emission control in future ammonia-fueled engines". 

The team emphasizes that while the API strategy is highly effective, further optimization of combustion chamber geometry and ammonia injection hardware will be critical for practical, large-scale industrial application. 

Journal: ENGINEERING Energy

Read the full article for free:  https://rdcu.be/frN5b

Cite this article: Yang, R., Yu, Z., Li, J. et al. In-cylinder NOx active reduction via ammonia post-injection in ammonia direct-injection engines. ENGINEERING Energy 20, 10798 (2026). https://doi.org/10.1007/s11708-026-1079-8

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Journal

ENGINEERING Energy

DOI

10.1007/s11708-026-1079-8 

Article Title

In-cylinder NOx active reduction via ammonia post-injection in ammonia direct-injection engines

Article Publication Date

15-Jun-2026

Antibiotic resistant gene found in Australian soil

A new study published in Nature Communications reveals a hidden source of antibiotic resistance, providing an early warning sign for researchers and public health officials. 

The novel gene found in contaminated freshwater NSW sediment, by researchers at Macquarie University and The University of Sydney, provides bacteria with resistance to polymyxin - a critical last line antibiotic, used when others stop working. 

The mcr-12 gene is the firt of its kind to be discovered outside a clinical, food or livestock setting. It’s also the first to be initially found outside a non-Gammaproteobacterial host (such as E. coli) and the first in the Southern Hemisphere. Scientists discovered mcrgenes only a decade ago, and since then believed they were only found in bacteria from hospitals, patients or livestock. 

“Polymyxin resistance genes are typically associated with settings where there has been direct antibiotic exposure, so this discovery challenges our previous assumptions,” says Dr Brodie Gillieatt, the lead researcher from Macquarie University.  

Concerningly, the gene still worked when it moved from its original host to several different pathogenic bacteria, - a problem if the gene spread to a clinical setting.  

Professor of Microbiology at Macquarie University, Amy K. Cain says the discovery is timely. “The gene has not yet spread to major human pathogens. Detecting it now, gives researchers and public health officials a chance to monitor its spread before it becomes a widespread clinical problem.” 

The gene was also found to be associated with heavy metal resistance genes in freshwater, contaminated by heavy metals - raising the possibility that metal pollution could help maintain antibiotic resistance genes. 

“It highlights the role of environmental pollution in antibiotic resistance meaning environmental management may also play a role in slowing the spread,” says Dr Gillieatt.  “These types of resistance genes are likely circulating in wider environmental reservoirs, and we simply have not invested in their detection until now. We need broader surveillance.” 

Research priorities are now focused on mapping where the gene occurs and testing if and how mcr-12 could mobilise.  

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Journal

Nature Communications

Method of Research

Experimental study

Article Title

Novel polymyxin resistance gene family mcr-12 from environmental Pigmentiphaga litoralis

Article Publication Date

15-Jul-2026

Sweeteners shown to slow growth of important gut bacteria in lab tests

University of Cambridge

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Cambridge researchers have shown how commonly-used sweeteners slow the growth of certain gut bacteria. One sweetener in particular – isosteviol – when combined with the anti-depressant duloxetine significantly impaired two important gut bacteria linked to regulating blood sugar and gut health and may affect the body’s immune responses.

The scientists say more research is needed to understand the real-world health impacts of this laboratory study, one of the first to assess the direct impact of sweeteners on gut bacteria, particularly when they are combined with other substances.

Sweeteners are widely used in a range of food and drinks, including soft drinks, sweets, desserts, snacks and cereals. While marketed as healthier alternatives to sugar, there is increasing evidence of links to diseases such as type 2 diabetes, obesity and cancer.

Despite their pervasive use, there have been very few studies that look at the direct interactions between sweeteners and gut bacteria – the vast community of microorganisms that live in the digestive tract and play a crucial role in keeping our bodies healthy.

Professor Kiran Patil from the Medical Research Council (MRC) Toxicology Unit at the University of Cambridge said: “Most of what we know about the potential impact of sweeteners on our health comes from animal research or from population studies. While these studies have indicated involvement of the microbiome in mediating the effect of sweeteners, it’s difficult to know how sweeteners act in the body – is it through direct interactions with our gut bacteria?”

“Answering this is further complicated by the fact that we rarely ever take sweeteners by themselves – we take them with drinks, in snacks, or even in medication to mask bitterness,” added Dr Sonja Blasche, a lead author of the study, also the MRC Toxicology Unit.

In research published in Molecular Systems Biology, Dr Blasche and colleagues looked at how artificial and low‑calorie sweeteners affect the bacteria living in our gut, and how these effects change when sweeteners are consumed together with other common substances such as caffeine, flavourings or medicines.

The researchers grew each of 25 gut bacterial species – including beneficial, neutral, and potentially harmful bacteria – in the lab. They then exposed each culture individually to 39 common, commercially-used sweeteners, some of which are artificial, others natural, and measured how well the bacteria multiplied.

Around three‑quarters of the sweeteners changed how at least one bacterial species grew. Some sweeteners slowed down or stopped the growth of certain bacteria linked to a healthy gut.

The researchers then tested each sweetener in combination with common compounds such as caffeine, vanillin (vanilla extract), advantame (an artificial sweetener) and eight commonly-used drugs to assess whether this had any impact on the gut bacteria. They found over 100 interactions where sweeteners acted differently when combined with other substances. In 34 cases, combinations made the effects stronger, while in 68 cases the effects were weaker.

Most striking was the combination of a sweetener called isosteviol, widely used in the food and beverage industry, and the antidepressant duloxetine. This combination strongly suppressed Roseburia intestinalis and Parabacteroides merdae, two gut bacteria that play important roles in maintaining a healthy digestive system. In the US in 2023, over 4.2 million patients were prescribed duloxetine.

As no gut bacterium exists alone, but rather as part of a ‘community’ within the gut, the researchers created a synthetic community containing all 25 bacteria. After allowing it to grow over time, they tested the community against a variety of sweetener and drug combinations, looking at which species increased or decreased and whether the overall diversity changed.

By mimicking in this simplified way what might happen in the human gut, they showed that the combination of isosteviol and duloxetine reduced microbial diversity. A diverse microbiome is considered important for good gut health. The sweetener-drug combination also altered which bacterial species thrived or declined.

Further analysis showed that the effect of the isosteviol-duloxetine combination on the community increased toxicity towards certain host cells and interfered with other cells that play a role in the body’s inflammation and immune responses.

Dr Blasche said: “Sweeteners are often marketed as metabolically neutral, but our study challenges this idea. We found that they can directly affect gut bacteria, particularly when mixed with other compounds such as medication and food additives. These common combinations could have unintended effects on our gut microbiome.”

The researchers stress that, as their experiments were carried out in the lab, not tested in humans, more research needs to be done before it is possible to conclude that there will be direct health effects in people.

Professor Patil, the study’s senior author, added: “Our study suggests that artificial sweeteners don’t just pass through the body passively — they can interact with gut microbes, and these effects can be amplified or altered by other substances like medications. These findings can help guide new studies towards understanding how sweeteners might influence health in unexpected ways.”

The research was funded by the European Union’s Horizon 2020 programme and the UK Medical Research Council.

Reference

Blasche, S. et al. Common xenobiotics modulate gut microbial responses to low‑calorie sweeteners in vitro. MSB; 25 Jun 2026; DOI: 10.1038/s44320-026-00225-6

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DOI

10.1038/s44320-026-00225-6 

Method of Research

Experimental study

Subject of Research

Cells

Article Title

Common xenobiotics modulate gut microbial responses to low‑calorie sweeteners in vitro

 

Loneliness strongly linked to poorer mental health and wellbeing, study finds

University of Bristol

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People who feel lonely are much more likely to experience poorer mental health and lower wellbeing, a new collaborative study led by the University of Bristol, Nesta and Amsterdam UMC has found. Loneliness was also found to be linked with worse general health, including experiencing multiple health conditions. Social isolation is associated with lower wellbeing, too.

Loneliness is increasingly recognised as a major public health issue, with growing evidence connecting it to poorer health. However, it is unclear whether loneliness itself contributes to poor health or whether these links are driven by other factors.

The study, in association with the universities of Oxford and Manchester, combined evidence from three different research methods, including observational analysis, sibling comparisons, and Mendelian randomisation, a genetics-based approach, to build a clearer understanding of these relationships.

Using data from the UK Biobank and large-scale genome-wide association studies, the researchers investigated how both loneliness - the quality of a person's social relationships; and social isolation - the number of social connections, relate to health and wellbeing. The study is published in Nature Communications today [15 July].

The research team found that loneliness and social isolation are linked to poorer mental health and reduced wellbeing, with loneliness also associated with worse general health. While the study found no clear evidence of effects on specific physical health conditions, these potential impacts cannot be ruled out.

The findings suggest that loneliness, and potentially social isolation, remain important public health issues, particularly because of their links with mental health, wellbeing and overall health.

As loneliness becomes an increasingly important public health challenge, tackling it could bring benefits for both individuals and society.

Dr Zoe Reed, Research Fellow in the School of Psychology and Neuroscience at the University of Bristol, and corresponding author, said: “Our findings suggest that loneliness, and possibly social isolation, are still important public health concerns, especially for mental health and general health. Supporting people who feel lonely or socially isolated could help improve mental health, wellbeing and overall health.”

Lauren Bowes Byatt, Director of Nesta’s healthy life mission, added: “This research underlines that loneliness is likely to have a detrimental impact on our mental health and wellbeing. While this link may seem obvious, the topic has long been understudied. Studies like this can help to bridge this research gap and by understanding how loneliness or social isolation may be contributing to ill-health, we can get closer to new and more effective solutions.”

The researchers suggest more research is needed to understand exactly how loneliness and social isolation affect health and to develop the most effective ways to reduce their impact.

As the study focused on middle-aged and older adults, future studies should explore whether these patterns are similar in younger people. It will also be important to investigate the effects of persistent or long-term loneliness, as the study measured loneliness at a single point in time.

The paper’s findings add to growing evidence that loneliness and social isolation are not just social issues, they are important public health concerns with wide-ranging implications for wellbeing and mental and physical health. The research reinforces the importance of addressing these issues as part of public health policy and practice.

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Journal

Nature Communications

DOI

10.1038/s41467-026-74758-7 

Method of Research

Observational study

Subject of Research

People

Article Title

Investigating relationships between loneliness, social isolation and health

Article Publication Date

15-Jul-2026

Loneliness is making people sick. Doctors can't cure it alone

University of Michigan

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While loneliness has been shown to harm one's health, framing it as a health issue shifts responsibility from society to healthcare, even though healthcare alone cannot rebuild social ties, a new University of Michigan study warns.

 

The study, published in Social Problems, documents how chronic loneliness and social isolation gained traction as public health concerns once research linked them to higher risks of disease, death and rising healthcare costs. 

 

Prior research discussed in the current study estimated that a lack of social connection is comparable to smoking 15 cigarettes a day. Another study found that social isolation, loneliness and living alone each raise the risk of premature death by roughly 30%. A third showed that beyond the physical toll, this experience may carry an economic price tag, costing Medicare an estimated $6.7 billion annually in elder care.

 

"Once people saw these findings, they began to treat loneliness as urgent," said U-M doctoral student Sofia Hiltner. "But it made me wonder: Why do we only consider problems important once they are tied to health?"

 

Hiltner interviewed experts and analyzed more than a decade's worth of media, medical journal articles and academic papers. She found that while linking loneliness to health gave the issue legitimacy, it also created what she calls a "logical leap"—the assumption that because a problem is related to health, the healthcare system should try to fix it.

 

"Not everything that relates to health belongs in healthcare," she said. "Doctors can screen patients and connect them to services, but they cannot rebuild communities or shorten work hours."

 

Hiltner, a predoctoral trainee in social demography at the Population Studies Center at U-M's Institute for Social Research, began studying loneliness after watching her grandmother become increasingly isolated later in life. When she started graduate school to study isolation among older people, she discovered clinical trials for a "loneliness pill". This experience raised questions about why loneliness is predominantly framed as a medical issue instead of a social one.

 

"After my grandfather died, my grandmother lived alone and there was little structure in her life," Hiltner said. "She didn't seem to have many friends or activities. It made me think about everything that happened throughout her life that led to that point. I wondered about the social policies, in addition to dynamics at the family level, that could have helped prevent that situation."

 

Cure may lie far outside the clinic

 

Hiltner's research also shows that members of the medical community did not initially want to claim loneliness as their responsibility. Instead, a mix of academic researchers, government health officials,and insurance companies pushed the issue into healthcare.

 

"There is the risk that defining loneliness as medical crowds out other ways of responding to the issue," she said. "Attention, time and resources are limited. On the other hand, framing it as medical may inspire more action than would have otherwise happened."

 

Hiltner hopes the study inspires policymakers to reflect on why they frame problems in certain ways and to consider upstream solutions.

 

"I would like them to reflect on the strengths and limitations of addressing problems through the healthcare system, and look farther upstream to understand how a problem emerges, considering ways to intervene before it occurs," she said. "Healthcare can help, but it can only go so far."

 

Study: The Medicalization of Loneliness: Addressing Social Ills Through Healthcare (DOI: 10.1093/socpro/spag034)

 

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Journal

Social Problems