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Researchers at the Max-Born-Institute have now mapped the linear and nonlinear optical polaron response using ultrafast two-dimensional spectroscopy in the THz frequency range. As they discuss in the current issue of Physical Review Letters, multi-photon ionization of isopropanol molecules by a femtosecond pulse in the near-infrared generates free electrons and the resulting changes of the dielectric properties of the liquid are probed and/or manipulated in the THz frequency range.

An electron and the surrounding cloud of solvent dipoles couple through electric forces and can undergo joint collective motions. Such many-body excitations in the terahertz (THz) frequency range are called polarons and have remained nearly unexplored so far. New results from ultrafast THz spectroscopy demonstrate the generation and manipulation of coherent polaron oscillations in a time range of 100 ps and beyond, thus enabling the control of dynamic electric properties of polar liquids.

Ionization of a polar liquid by intense light or particle beams generates free electrons, which relax on a picosecond timescale (1 ps = 10^-12 s) into a localized ground state. The relaxation process includes the reorientation of the surrounding dipolar solvent molecules and the dissipation of excess energy.

Whenever light interacts with matter, light appears to slow down. This is not a new observation and standard wave mechanics can describe most of these daily phenomena.

For example, when light is incident on an interface, the standard wave equation is satisfied on both sides. To analytically solve such a problem, one would first find what the wave looks like at either side of the interface, and then employ electromagnetic boundary conditions to link the two sides together. This is called a piecewise continuous solution.

However, at the boundary, the incident light must experience an acceleration. So far, this has not been accounted for.

You may not realize it, but the Doppler effect is everywhere in our lives, from tracking the speed of cars with radar to locating satellites in the sky. It’s all about how waves change their frequency when a source (like a radar signal) and a detector are in motion relative to each other. However, traditional radar systems hit a roadblock when trying to detect objects moving at right angles to their radar signals. This limitation has driven researchers to explore an entirely new approach.

Imagine a radar system that doesn’t just rely on linear waves but instead uses spiraling electromagnetic waves with orbital angular momentum (OAM). These special “vortex” waves have a helical twist and introduce a signature rotational Doppler effect when they encounter a spinning object.

To improve identification and detection of these rotational Doppler effects, researchers from University of Shanghai for Science and Technology (USST) have harnessed terahertz (THz) waves by developing an integrated THz vortex beam emitter, as reported in Advanced Photonics.

A team of researchers led by the University of California San Diego has developed soft yet durable materials that glow in response to mechanical stress, such as compression, stretching or twisting. The materials derive their luminescence from single-celled algae known as dinoflagellates.

The work, inspired by the bioluminescent waves observed during red tide events at San Diego’s beaches, was published Oct. 20 in Science Advances.

“An exciting feature of these materials is their inherent simplicity—they need no electronics, no external power source,” said study senior author Shengqiang Cai, a professor of mechanical and aerospace engineering at the UC San Diego Jacobs School of Engineering. “We demonstrate how we can harness the power of nature to directly convert mechanical stimuli into light emission.”

The human brain is made up of two kinds of matter: the nerve cell bodies (gray matter), which process sensation, control voluntary movement, and enable speech, learning and cognition, and the axons (white matter), which connect cells to each other and project to the rest of the body.

Historically, scientists have concentrated on the gray matter of the cortex, figuring that’s where the action is, while ignoring white matter, even though it makes up half the brain. Researchers at Vanderbilt University are out to change that.

For several years, John Gore, Ph.D., director of the Vanderbilt University Institute of Imaging Science, and his colleagues have used functional magnetic resonance imaging (fMRI) to detect blood oxygenation-level dependent (BOLD) signals, a key marker of brain activity, in white matter.

The limitless world of chemistry and how researchers investigate it.

This model of computing would use 1/1000th of the energy today’s computers do. So why aren’t we using it?

Influenza viruses are believed to have sparked at least 14 human pandemics in the past 500 years; the most devastating of which began in 1918. Yet, despite intense study and considerable advances in public health, virus surveillance and virology, there is no simple answer to this pressing question: when and how will the next flu pandemic arise?

NIAID scientists including Jeffery K. Taubenberger, M.D., Ph.D., consider the many potential pathways to future influenza pandemics in a new viewpoints essay in Science Translational Medicine. There are no hard and fast ‘rules’ specifying, for example, what characteristics a given avian influenza virus must possess to allow it to efficiently infect… More.

Influenza pandemics have emerged for centuries but still cannot be accurately predicted.

A NIAID-funded study suggests a strategy to mitigate harmful side effects of nanoparticles in medicine. The researchers showed in animal models that a lab-made molecule safely prevented nanomedicines from activating a set of immune-system proteins called the complement system and causing negative side effects. This is significant because when nanoparticles activate complement, the resulting immune response can not only cause an adverse reaction, but also reduce the efficacy of nanomedicines.