Manipulating light at extremely small scales is key to advancing modern technology. As traditional electronics begin to reach their limits, photonics offers an alternative by using light instead of electrons to carry information. Because photons move faster and do not have mass like electrons, devices based on light could become both quicker and smaller, opening the door to more powerful and compact technologies.

The Challenge of Light’s Wavelength

Light behaves both as a particle and as a wave, and this wave nature introduces a limitation. Each type of light has a wavelength, which determines how small a structure can be while still controlling it effectively. Visible light has wavelengths of several hundred nanometers, while infrared light extends to a micrometer or more. This raises an important question: can light be confined in structures smaller than its own wavelength?

The research team demonstrated that this is indeed possible. By engineering a subwavelength grating, they were able to trap infrared light within a layer only 40 nanometers thick. This structure consists of closely spaced parallel strips that interact with light similarly to a prism. When these strips are positioned closer together than the wavelength of light, the grating can act like a near-perfect mirror while also holding the light inside a very small volume.

Why Molybdenum Diselenide Works So Well

Earlier versions of such gratings, made from materials like silicon or gallium compounds, required thicknesses of several hundred nanometers to function effectively. Reducing their size caused them to lose their ability to confine light. The key difference in this new approach is the use of molybdenum diselenide, which has a much higher refractive index. In simple terms, light slows down more inside this material than in others. While light slows by about 1.5 times in glass and roughly 3.5 times in silicon or gallium arsenide, it slows by about 4.5 times in MoSe₂. This strong slowing effect allows the structure to shrink dramatically while still trapping light efficiently, resulting in a layer more than a thousand times thinner than a human hair.

Turning Infrared Light Into Blue Light

MoSe₂ also brings additional advantages. Like graphene, it forms layered structures, but unlike graphene, it is a semiconductor. It also exhibits nonlinear optical behavior, including a process known as third harmonic generation. In this process, three infrared photons combine into one photon with a higher frequency, effectively converting infrared light into visible blue light. Because the grating strongly concentrates infrared light, this conversion becomes much more efficient. The researchers found that the effect is more than 1,500 times stronger compared to a flat layer of the same material.

Another major advance lies in how the material was produced. Previously, thin layers of MoSe₂ were created using exfoliation — a method similar to peeling layers off a crystal with adhesive tape. While simple, this technique is inconsistent and limited to very small areas, typically around ten square micrometers, which is not suitable for real-world devices.

To overcome this, the team used molecular beam epitaxy (MBE), a well-established method for growing semiconductor layers. This approach allowed them to produce large, uniform MoSe₂ films spanning several square inches. Despite this large size, the layer maintained a thickness of just 40 nanometers, giving it an extreme aspect ratio. For comparison, the thickness-to-size ratio of this layer is about one to a million, while a typical A4 sheet of paper has a ratio closer to 1:2000.

Toward Practical Photonic Applications

These results suggest that molybdenum diselenide produced in this way could significantly change how light is controlled in future technologies. Structures no longer need to be thick to manipulate light effectively. Instead, extremely thin layers can perform the same function, and in some cases even better. Because the production method is scalable, the path toward real-world applications, such as photonic integrated circuits, is becoming increasingly realistic.

Funding and Support

The research was funded by the National Science Centre under projects OPUS 2020/39/B/ST7/03502 and 2021/41/B/ST3/04183, with European Union funds under ERC-ADVANCED grant No. 101053716, the Foundation for Polish Science under project ENG.02.01-IP.05-T004/23, and by the University of Warsaw under the Excellence Initiative – Research University (IDUB) New Ideas in Priority Research Areas II No. 501-D111-20-2004310 titled “Ultrathin subwavelength gratings based on dichalcogenides.”

The team examined a region of Alaska’s North Slope roughly the size of Wisconsin, where hundreds of rivers and streams drain into the Beaufort Sea. Using 44 years of model data at a resolution of one kilometer, they found that runoff is rising sharply, rivers are carrying increasing amounts of carbon, and the thaw season is extending later into the year, now reaching late summer and fall. The findings were published in Global Biogeochemical Cycles.

Arctic Rivers Play an Outsized Role in the Global System

Rivers in the Arctic have a surprisingly large influence on the planet. They deliver about 11% of the world’s river water into an ocean that holds just 1% of global ocean volume. This makes the Arctic Ocean especially sensitive to changes occurring in rivers and streams across the region.

Although melting snow supplies much of this water, thawing permafrost is becoming increasingly important. The ground contains a layer known as the “active layer,” which freezes and thaws each year. As the climate warms, this layer is getting deeper, allowing more groundwater to flow into Arctic rivers.

Thawing Soil Is Releasing Ancient Carbon

The active layer holds large quantities of organic material that have been frozen for thousands of years. As it deepens, more of this material is released into rivers as dissolved organic carbon (DOC), eventually reaching the ocean.

The Arctic Ocean already receives a disproportionate share of this carbon compared to other parts of the world. Each year, more than 275 million tons of it are converted into carbon dioxide, adding to global warming and creating a feedback loop that can intensify climate change.

Limited Observations Make Modeling Essential

Understanding how individual rivers respond to warming is challenging because direct measurements in northern Alaska are limited.

“What makes this question so hard to answer is that direct observations are very sparse in northern Alaska,” says Rawlins, extension associate professor of Earth, Geographic, and Climate Sciences at UMass Amherst. “There are nowhere near enough river sample measurements to quantify inputs to estuaries along the entire Alaskan North Slope.”

To address this gap, Rawlins developed the Permafrost Water Balance Model over the past 25 years. This model estimates key processes such as snow accumulation, melt, and changes in the active layer to better represent real conditions. In 2021, it was expanded to simulate dissolved organic carbon, and in 2024 it was applied across 22.45 million square kilometers of Arctic land.

The model suggests that over the next 80 years, the Arctic could experience up to 25% more runoff, 30% more subsurface flow, and increasing dryness in southern areas.

High-Resolution Modeling Reveals New Patterns

Previous versions of the model used grid cells that were 25 kilometers wide. This study improves on that by capturing changes at a much finer scale.

“We’ve typically run the model on 25-kilometer grid cells,” says Rawlins. “This new study is the first time anyone has captured such a wide area of the Arctic — about the size of Wisconsin — down to the kilometer scale, and over such a long period of time: our model simulates daily river flows and coastal exports over 44 years from 1980 to 2023.”

Running the model required substantial computing power. Each simulation took 10 continuous days on a supercomputer at the Massachusetts Green High Performance Computing Center.

“Our freshwater and DOC inputs to coastal estuaries will be useful to a broad range of stakeholders interested in these unique ecosystems in coastal northern Alaska,” says Rawlins, “including the Beaufort Lagoon Ecosystems project, which is helping to quantify exactly what’s coming through these coastal estuaries.”

Northwest Alaska Shows the Biggest Carbon Increases

The researchers found that while runoff and thawing are increasing across the region, the largest rise in carbon export is occurring in northwest Alaska.

“It’s flatter over there,” says Rawlins, “which means there’s much more carbon from decaying matter in the permafrost that has been accumulating for tens of thousands of years. This is ancient carbon. The further east you go, the more mountainous it becomes. The soil is rockier and sandier, and so far less DOC is mobilized as the permafrost thaws.”

A Longer Thaw Season Is Driving Change

One of the most notable findings is how much of the change is tied directly to permafrost thaw. The thaw season now lasts longer than in the past, extending into September and even October.

These changes are likely affecting salinity, nutrient cycles, and food webs in the Beaufort Sea. Researchers are now studying how ice wedge polygons, a common Arctic landscape feature, influence how water and carbon move toward coastal areas.

A Critical Gap in Understanding the Carbon Cycle

“How much DOC finds its way to the ocean via rivers and streams is a part of the carbon cycle we don’t know much about,” says Rawlins. “We desperately need more of these land-to-ocean connection studies if we’re to fully grapple with the problem of global warming and the effects it will have on coastal ecosystems.”

The research was supported by the U.S. National Science Foundation and NASA.

New research suggests otherwise, according to a Keck Medicine of USC study published today in Clinical Gastroenterology and Hepatology. 

Researchers discovered that people with metabolic dysfunction–associated steatotic liver disease (MASLD), the most common liver condition in the country affecting one-in-three adults, face significantly higher risk of liver fibrosis, or harmful scarring of the liver, if they engage in episodic heavy drinking. Episodic heavy drinking is four or more drinks in one day for women and five or more drinks in one day for men, at least once a month. 

Those who consume large amounts of alcohol in a single day at least once per month are three times more likely to develop advanced liver fibrosis than individuals who spread out the same total alcohol intake over time, according to the findings. 

Younger adults and men were more likely to report episodic heavy drinking, and the more drinks consumed at one time, the more liver fibrosis people tended to have. 

“This study is a huge wake-up call because traditionally, physicians have tended to look at the total amount of alcohol consumed, not how it is consumed, when determining the risk to the liver,” said Brian P. Lee, MD, MAS, a hepatologist and liver transplant specialist with Keck Medicine and principal investigator of the study. “Our research suggests that the public needs to be much more aware of the danger of occasional heavy drinking and should avoid it even if they drink moderately the rest of the time.”  

How the study was conducted 

Lee and his colleagues used data from the nationally representative National Health and Nutrition Examination Survey, a long-running health survey of the United States population. They included data from more than 8,000 adults, collected between 2017 and 2023. In particular, they looked at the link between episodic heavy drinking and advanced liver fibrosis to understand how drinking patterns — not just total drinks — may cause harm even to moderate drinkers, which is considered seven drinks a week for women and 14 or less for men.  

The research team focused on MASLD because of its prevalence among Americans. MASLD affects people with excess weight, obesity or other metabolic conditions, such as Type 2 diabetes, high blood pressure or high cholesterol, and is on the rise. Additionally, while MASLD is not defined as alcohol-related, Lee and his colleagues wanted to explore if alcohol did in fact play some role in the condition. 

More than one-half of the adults included in the study reported episodic heavy drinking and almost 16% of patients with MASLD were episodic heavy drinkers. 

The researchers compared people with MASLD with the same age, sex and average weekly alcohol consumption, segmenting some as episodic heavy drinkers and others as non-episodic heavy drinkers, to reach their conclusion that episodic heavy drinkers with MASLD had nearly three times higher odds of experiencing advanced liver fibrosis.  

Lee speculates that episodic heavy drinking can harm the liver both directly and indirectly. Drinking large amounts of alcohol at once can overwhelm the liver and increase inflammation, which leads to scarring and damage. People with MASLD may be particularly at risk, as Lee’s previous research has shown that obesity, high blood pressure and other conditions associated with MASLD can more than double liver disease risk. 

Alcohol-related liver disease has more than doubled in the last two decades, according to Lee. He believes this trend is driven by pandemic-era surges in drinking and an increase in people with risk factors for MASLD, like obesity and diabetes.  

“Although this study focused on patients with MASLD, these findings may also be pertinent to a broader patient population,” said Lee. “With more than half of adults reporting some episodic heavy drinking, this issue deserves further attention from both physicians and researchers to help better understand, prevent and treat liver disease.” 

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For more information about Keck Medicine of USC, please visit news.KeckMedicine.org. 

The study was supported by a grant from the National Institute on Alcohol Abuse and Alcoholism, grant number K23AA029752. 

High blood pressure (hypertension) affects about 1.3 billion people worldwide. In nearly half of these cases, the condition is either uncontrolled or does not respond well to treatment. This greatly increases the risk of heart attack, stroke, kidney disease, and early death. In the UK alone, around 14 million people are living with hypertension.

Large International Trial of Baxdrostat

The international BaxHTN trial, led by Professor Bryan Williams (UCL Institute of Cardiovascular Science) and funded by AstraZeneca, tested a new drug called baxdrostat, which is taken as a tablet. The study included nearly 800 patients across 214 clinics around the world.

The research was supported by the NIHR Biomedical Research Centre at UCLH.

The results were presented at the European Society of Cardiology (ESC) Congress 2025 in Madrid and were also published in the New England Journal of Medicine.

Significant Blood Pressure Reductions

After 12 weeks, patients taking baxdrostat (1 mg or 2 mg once daily in pill form) experienced an average drop in blood pressure of about 9 to 10 mmHg more than those taking a placebo. This level of reduction is considered large enough to lower the risk of cardiovascular events.

Around 40 percent of patients taking baxdrostat reached healthy blood pressure levels, compared with fewer than 20 percent in the placebo group.

Principal Investigator, Professor Williams, who is presenting the results at ESC, said: “Achieving a nearly 10 mmHg reduction in systolic blood pressure with baxdrostat in the BaxHTN Phase III trial is exciting, as this level of reduction is linked to substantially lower risk of heart attack, stroke, heart failure and kidney disease.”

How Baxdrostat Targets a Key Hormone

Blood pressure is heavily influenced by a hormone called aldosterone, which helps regulate salt and water levels in the body.

In some individuals, the body produces too much aldosterone. This leads to excess salt and water retention, raising blood pressure and making it difficult to control.

Scientists have long tried to address this imbalance, but it has proven challenging.

Baxdrostat works by blocking the production of aldosterone, directly targeting a major cause of high blood pressure (hypertension).

A New Approach to Difficult Cases

Professor Williams, Chair of Medicine at UCL, said: “These findings are an important advance in treatment and in our understanding of the cause of difficult to control blood pressure.

“Around half of people treated for hypertension do not have it controlled, however this is a conservative estimate and the number is likely higher, especially as the target blood pressure we try to reach is now much lower than it was previously.^[1]

“In patients with uncontrolled or resistant hypertension, the addition of baxdrostat 1mg or 2mg once daily to background antihypertensive therapy led to clinically meaningful reductions in systolic blood pressure, which persisted up to 32 weeks with no unanticipated safety findings.

“This suggests that aldosterone is playing an important role in causing difficult to control blood pressure in millions of patients and offers hope for more effective treatment in the future.”

Rising Global Burden and Future Potential

In the past, higher rates of hypertension were mainly seen in wealthier Western countries. However, changing diets, including reduced salt intake in some regions, have shifted the global burden. Today, far more cases are found in Eastern and lower income countries. More than half of all people with hypertension live in Asia, including 226 million in China and 199 million in India.^[2]

Professor Williams added: “The results suggest that this drug could potentially help up to half a billion people globally — and as many as 10 million people in the UK alone, especially at the new target level for optimal blood pressure control.”

Notes

1. The ESC 2024 hypertension guidelines recommended a target blood pressure of less than 130/80 mmHg. Prior to 2024 the target had been 140/90 mmHg.
2. Figures from Blood Pressure UK