Rice researchers uncover the hidden physics of knot formation in fluids

From left to right, top to bottom: Sibani Lisa Biswal, Fred MacKintosh, Lucas H.P. Cunha and Luca Tubiana.
Photo Credit: Courtesy of Rice University

Knots are everywhere — from tangled headphones to DNA strands packed inside viruses — but how an isolated filament can knot itself without collisions or external agitation has remained a longstanding puzzle in soft-matter physics.

Now, a team of researchers at Rice University, Georgetown University and the University of Trento in Italy has uncovered a surprising physical mechanism that explains how a single filament, even one too short or too stiff to easily wrap around itself, can form a knot while sinking through a fluid under strong gravitational forces. The discovery, published in Physical Review Letters, provides new insight into the physics of polymer dynamics, with implications ranging from understanding how DNA behaves under confinement to designing next-generation soft materials and nanostructures.

“It is inherently difficult for a single, isolated filament to knot on its own,” said Sibani Lisa Biswal, corresponding author, chair of Rice’s Department of Chemical and Biomolecular Engineering and the William M. McCardell Professor in Chemical Engineering. “What’s remarkable about this study is that it shows a surprisingly simple and elegant mechanism that allows a filament to form a knot purely because of stochastic forces as it sediments through a fluid under strong gravitational forces.”

AI helps explain how covert attention works and uncovers new neuron types

Image Credit: Scientific Frontline / AI generated

Shifting focus on a visual scene without moving our eyes — think driving or reading a room for the reaction to your joke — is a behavior known as covert attention. We do it all the time, but little is known about its neurophysiological foundation. Now, using convolutional neural networks (CNNs), UC Santa Barbara researchers Sudhanshu Srivastava, Miguel Eckstein and William Wang have uncovered the underpinnings of covert attention and, in the process, have found new, emergent neuron types, which they confirmed in real life using data from mouse brain studies. 

“This is a clear case of AI advancing neuroscience, cognitive sciences and psychology,” said Srivastava, a former graduate student in the lab of Eckstein, now a postdoctoral researcher at UC San Diego. 

Climate shapes arms race between ants and their social parasites

The "slave-making ant" Temnothorax americanus (left) and its host Temnothorax longispinosus
Photo Credit: ©: Romain Libbrecht

The battle between ant hosts and their social parasites is strongly influenced by climate. Temperature and humidity shape how the ants behave, communicate, and even evolve — while host and parasite respond with very different genetic strategies. These are the findings of two recent studies in which researchers at Johannes Gutenberg University Mainz (JGU) and the Senckenberg Biodiversity and Climate Research Centre combined behavioral experiments with state-of-the-art genomic analyses. "Climate clearly explains the variation in host and parasite behavior better than parasite prevalence itself," says Professor Susanne Foitzik, senior author of both studies and chair of Behavioral Ecology and Social Evolution at JGU.

In the first study, published in the Journal of Evolutionary Biology, the team examined a parasite, the so-called "slave-making ant" Temnothorax americanus, and its host, the ant Temnothorax longispinosus. The social parasite invades host nests and steals their brood, which later grows up to work for the parasite colony – an extraordinary form of social parasitism. The researchers focused on how the ants' behavior and chemical communication vary across different climates. By comparing ten natural populations along a 1,000‑kilometer north-south gradient in the United States, they found that climate influenced the conflict more strongly than the local frequency of parasite colonies.

Biodegradable wet wipes remain in rivers for more than five weeks

Photo Credit: Christine Sandu

Scientists have tested, for the first time, how biodegradable wet wipes break down when flushed rather than composted discovering that most wipes remain after five weeks – a finding the research team says challenges the marketing of these products. 

Researchers from Cardiff University’s Schools of Biosciences, Chemistry and Engineering tested two widely available brands of wipes labelled as ‘biodegradable’ in ten urban rivers and streams in Cardiff, UK 

For five weeks, the team tracked the degradation of the wet wipes in these locations by testing their tensile strength loss, and recording environmental factors such as microbial biomass, water chemistry, temperature, and river-level fluctuations. 

Stroke and dementia: combating loss of function in small vessels of the brain

Professor Martin Dichgans
Photo Credit: © LMU / Stephan Höck

Researchers at LMU University Hospital have elucidated how diseases of small blood vessels in the brain develop. So-called cerebral small vessel disease (CSVD) can lead to widespread consequences such as circulatory disorders, hemorrhages, and often severe strokes, and is considered one of the main causes of dementia. The scientists' results have now been published in the journal Nature Neuroscience. 

In view of the prevalence of this serious and life-threatening condition—strokes, for example, are the leading cause of long-term disability and the second leading cause of death—it is astonishing "that medicine has so far known comparatively little about the cellular and molecular mechanisms underlying the development of cerebral small vessel disease," says LMU Professor Martin Dichgans, Chair of Translational Stroke and Dementia Research, Director of the Institute for Stroke and Dementia Research (ISD) at LMU University Hospital Munich, and future spokesperson for the SyNergy Cluster of Excellence. 

Fine particles in pollution are associated with early signs of autoimmune disease

Photo Credit: Chris LeBoutillier

A new study has linked air pollution exposure and immune-system changes that often precede the onset of autoimmune diseases. 

McGill University researchers analyzing Ontario data found that fine particles in air pollution are associated with higher levels of a biomarker linked with autoimmune diseases, such as systemic lupus. 

“These results point us in a new direction for understanding how air pollution might trigger immune system changes that are associated with autoimmune disease,” said Dr. Sasha Bernatsky, a James McGill Professor of Medicine and member of the McGill Centre for Climate Change and Health, the Division of Rheumatology and the Centre for Outcome Research and Evaluation. “We know some genetic factors play a role in autoimmune disease, but they don’t tell the whole story.” 

Lowering blood sugar cuts heart attack risk in people with prediabetes

Lowering blood sugar levels halves the likelihood of serious heart problems in people with prediabetes.
Photo Credit: isens usa

According to King’s College London research, published in The Lancet Diabetes & Endocrinology, bringing blood glucose back to normal levels - effectively reversing prediabetes - cuts the risk of death from heart disease or hospital admission for heart failure by more than 50%. 

This finding is especially important considering recent research showing that lifestyle changes alone - including exercise, weight loss and dietary improvements - do not lower cardiovascular risk in people with prediabetes. 

Together, these discoveries present a new, life-saving target for prediabetes and the prevention of cardiovascular disease; while potentially signaling a paradigm change for the way these conditions are treated by clinicians. 

Electrodes created using light

Researcher at LiU have developed a technique where visible light can be used to create electrodes from conductive plastics completely without hazardous chemicals. The technique requires no advanced laser setups – visible light from simple LED lamps, such as a party light, can drive the polymerization. 
Photo Credit: Thor Balkhed

Visible light can be used to create electrodes from conductive plastics completely without hazardous chemicals. This is shown in a new study carried out by researchers at Linköping and Lund universities. The electrodes can be created on different types of surfaces, which opens up for a new type of electronics and medical sensors. 

“I think this is something of a breakthrough. It’s another way of creating electronics that is simpler and doesn’t require any expensive equipment,” says Xenofon Strakosas, assistant professor at the Laboratory of Organic Electronics, LOE, at Linköping University. 

Scientists identify small RNA molecule that regulates cholesterol and heart disease

Xiuchun Li is the first author of the research paper.
Photo Credit: UCR/Zhou lab

A team of researchers led by University of California, Riverside biomedical scientists has identified a small, previously overlooked small RNA molecule that plays a major role in controlling the body’s cholesterol production and the development of heart disease. The molecule, named tsRNA-Glu-CTC, could be a potential new target for future therapies aimed at lowering high cholesterol.

Using PANDORA-seq, a sequencing technology developed at UC Riverside, the scientists were able to detect hidden types of small RNAs in the liver, the organ central to cholesterol metabolism. They found that tsRNA-Glu-CTC is highly abundant in the liver (more than 65% of all detectable tsRNAs or tRNA-derived small RNAs) and responds directly to changes in cholesterol levels. The study was done in mice.

The research established a direct link between tsRNA-Glu-CTC and SREBP2 (Sterol Regulatory Element-Binding Protein 2), a key protein known as the “master regulator” of cholesterol production.

Reproduced human neural circuits show the crucial role of the thalamus in shaping the cortical circuit

Assembloid [3D fluorescent staining] Axons in the thalamus (pink) extended toward the cortex, while those in the cortex (green) extended toward the thalamus at 14 days post-fusion.
Image Credit: Fumitaka Osakada

A Japanese research team has successfully reproduced the human neural circuit in vitro using multi-region miniature organs known as assembloids, which are derived from induced pluripotent stem (iPS) cells. With this circuit, the team demonstrated that the thalamus plays a crucial role in shaping cell type-specific neural circuits in the human cerebral cortex.

These findings were published in the journal Proceedings of the National Academy of Sciences of the United States of America.

Our brain’s cerebral cortex contains various types of neurons, and effective communication among these neurons and other brain regions is crucial for activating functions like perception and cognition.

Patients with neurodevelopmental disorders, such as autism spectrum disorder (ASD), exhibit disruptions in the structure and function of neural circuits in the cerebral cortex. Therefore, understanding the principles of these circuits is essential to uncovering the causes of these disorders and developing new medications.