Comment

Comment by Dr. Krishna Kumari Challa on January 30, 2024 at 11:07am

Researchers slow down light in metasurfaces with record low loss

The speed of light can be intentionally reduced in various media. Various techniques have been developed over the years to slow down light, including electromagnetically induced transparency (EIT), Bose-Einstein condensate (BEC), photonic crystals, and stimulated Brillouin scattering (SBS).

Notably, researchers from Harvard, led by Lene Vestergaard Hau, reduced light speed to 17 m/s in an ultracold atomic gas using EIT, which sparked the interest in exploring EIT analogs in metasurfaces, a transformative platform in optics and photonics.

Despite the benefits, slow-light structures face a significant challenge: Loss, which limits storage time and interaction length. This issue is particularly severe for metasurface analogs of EIT due to scattering loss of nanoparticles and sometimes absorption loss of materials.

In a study published in Nano Letters, researchers introduced a novel strategy to realize a metasurface analog of EIT while effectively suppressing losses.

Unlike conventional metasurface analogs of EIT induced by coupling between two localized resonances supported by closely packed meta-atoms, or between localized and collective resonances, the researchers proposed a new type called "collective EIT-like resonance," which is induced by the coupling between two collective resonances—a Mie electric dipole surface lattice resonance (ED-SLR) and an in-plane or out-of-plane electric quadrupole SLR (EQ-SLR).

Using silicon metasurfaces with a 100 nm-thick nanodisk array, they demonstrated collective EIT-like resonances with a quality factor exceeding 2,750, more than five times the state-of-the-art. In practical terms, light passing through the silicon nanodisks can be slowed down by more than 10,000 times, with a reduction in loss by more than five times compared to existing methods.

The departure from the conventional belief that metasurface performance depends on how closely meta-atoms can be placed. The researchers explored the extreme regime of zero distance between meta-atoms, essentially merging them into one. Unlike conventional methods, their approach allowed the tuning of surface lattice resonances to overlap spectrally, enabling the realization of metasurface analogs of EIT.

Furthermore, the researchers demonstrated a BIC-characterized collective EIT-like resonance utilizing the transition between the in-plane EQ-SLR and the bound state in the continuum (BIC). This suggested the potential to slow down light by an arbitrarily large factor while maintaining a growing quality factor.

 Xueqian Zhao et al, Ultrahigh-Q Metasurface Transparency Band Induced by Collective–Collective Coupling, Nano Letters (2024). DOI: 10.1021/acs.nanolett.3c04174

Comment by Dr. Krishna Kumari Challa on January 30, 2024 at 10:58am

Research reveals quantum entanglement among quarks

Collisions of high energy particles produce "jets" of quarks, anti-quarks, or gluons. Due to the phenomenon called confinement, scientists cannot directly detect quarks. Instead, the quarks from these collisions fragment into many secondary particles that can be detected.

Scientists recently addressed jet production using quantum simulations. They found that the propagating jets strongly modify the quantum vacuum—the quantum state with the lowest possible energy. In addition, the produced quarks retain quantum entanglement, the linkage between particles across distances. This finding, published in Physical Review Letters, means that scientists can now study this entanglement in experiments.

Adrien Florio et al, Real-Time Nonperturbative Dynamics of Jet Production in Schwinger Model: Quantum Entanglement and Vacuum Modification, Physical Review Letters (2023). DOI: 10.1103/PhysRevLett.131.021902

Comment by Dr. Krishna Kumari Challa on January 30, 2024 at 10:05am

How obesity dismantles our mitochondria: Study reveals key mechanism behind obesity-related metabolic dysfunction

The number of people with obesity has nearly tripled since 1975, resulting in a worldwide epidemic. While lifestyle factors like diet and exercise play a role in the development and progression of obesity, scientists have come to understand that obesity is also associated with intrinsic metabolic abnormalities.

Now researchers  have shed new light on how obesity affects our mitochondria, the all-important energy-producing structures of our cells.

In a study published in Nature Metabolism, the researchers found that when mice were fed a high-fat diet, mitochondria within their fat cells broke apart into smaller mitochondria with reduced capacity for burning fat. Further, they discovered that this process is controlled by a single gene. By deleting this gene from the mice, they were able to protect them from excess weight gain, even when they ate the same high-fat diet as other mice.

Caloric overload from overeating can lead to weight gain and also triggers a metabolic cascade that reduces energy burning, making obesity even worse.

In the case of caloric imbalances like obesity, the ability of fat cells to burn energy starts to fail, which is one reason why it can be difficult for people with obesity to lose weight.

In addition to discovering this metabolic effect, they also discovered that it is driven by the activity of a single molecule, called RaIA. RaIA has many functions, including helping break down mitochondria when they malfunction. The new research suggests that when this molecule is overactive, it interferes with the normal functioning of mitochondria, triggering the metabolic issues associated with obesity. In essence, chronic activation of RaIA appears to play a critical role in suppressing energy expenditure in obese adipose tissue. By understanding this mechanism, we're one step closer to developing targeted therapies that could address weight gain and associated metabolic dysfunctions by increasing fat burning.

 Nature Metabolism (2024). DOI: 10.1038/s42255-024-00978-0

Comment by Dr. Krishna Kumari Challa on January 30, 2024 at 9:48am

Coenobita purpureus with artificial shells: (A) plastic cap, (B) bulb fragment, (C) metal cap with a glass bottle fragment. Credit: Shawn Miller / Science of the Total Environment (2024). DOI:/10.1016/j.scitotenv.2023.168959

Part 3

Comment by Dr. Krishna Kumari Challa on January 30, 2024 at 9:46am

In discussing possible reasons for this behavior among Coenobitidae, the team notes the environmental availability of plastic waste, along with the growing scarcity of gastropod shells due to localized human activities. The researchers also suggest factors involved in individual choice, including:

• Attractiveness of artificial materials to mating females
• Lighter artificial shell weights that might benefit hermit crabs' energy
• An odor cue of dimethyl sulfide, found in both natural shells and marine waste; and
• The possibility that artificial shells may serve more efficiently as camouflage in polluted areas, given that shell selection is often made to blend into the localized environment.

These are all topics for further investigation.

"Are artificial shells setting the scene for a novel evolutionary trajectory in hermit crabs, or are they an ecological and evolutionary trap of the Anthropocene?" the researchers ask.

While this new behavior might be considered a clever adaptation, the main factor behind it is undeniable. In that vein, what this habit ultimately means for the evolution of terrestrial hermit crabs remains to be studied.

 Zuzanna Jagiello et al, The plastic homes of hermit crabs in the Anthropocene, Science of the Total Environment (2024). DOI:/10.1016/j.scitotenv.2023.168959

Part 2

Comment by Dr. Krishna Kumari Challa on January 30, 2024 at 9:45am

On tropical coasts, hermit crabs are now making their homes in plastic waste

Terrestrial hermit crabs are soft-bodied crustaceans that live near water in the world's tropical areas. Without any natural protection of their own, these crabs normally find shelter in discarded mollusk shells. But a number of terrestrial hermit crab species are beginning to opt for artificial shells frequently consisting of plastic objects found in beach trash.

New research on this topic, described in a short communication by a team from the University of Warsaw's Biological and Chemical Research Center and the department of Zoology at Poland's Poznań University of Life Sciences, appears in Science of the Total Environment.

Plastic pollution, which is increasing, already comprises 85% of marine pollution worldwide. Existing research shows that most of the plastic pollution in Earth's oceans arrives there via rivers, leading to plastic waste accumulation on coastlines.

Terrestrial hermit crabs (Coenobitidae) live on all the world's tropical coastlines, and typically acquire empty shells of gastropods to protect their soft abdominal region, known as pleon. The shells protect them from predators and also keep their pleon from drying out.

Studies on the crabs' selection of shells have shown the main factors include chemical signals gleaned from shells; proximity of predators; quality of shells; and rate of individual crab growth. It has also been shown that shells play a role in sexual signaling, as the size and state of male crabs' shells affect females' mate choices.

Part 1

Comment by Dr. Krishna Kumari Challa on January 27, 2024 at 11:35am

Writing by hand may increase brain connectivity more than typing on a keyboard

As digital devices progressively replace pen and paper, taking notes by hand is becoming increasingly uncommon in schools and universities. Using a keyboard is recommended because it's often faster than writing by hand. However, the latter has been found to improve spelling accuracy and memory recall.

To find out if the process of forming letters by hand resulted in greater brain connectivity, researchers  now investigated the underlying neural networks involved in both modes of writing.

They showed that when writing by hand, brain connectivity patterns are far more elaborate than when typewriting on a keyboard. Such widespread brain connectivity is known to be crucial for memory formation and for encoding new information and, therefore, is beneficial for learning.

The researchers collected EEG data from 36 university students who were repeatedly prompted to either write or type a word that appeared on a screen. When writing, they used a digital pen to write in cursive directly on a touchscreen. When typing they used a single finger to press keys on a keyboard.

High-density EEGs, which measure electrical activity in the brain using 256 small sensors sewn in a net and placed over the head, were recorded for five seconds for every prompt.

Connectivity of different brain regions increased when participants wrote by hand, but not when they typed. These findings suggest that visual and movement information obtained through precisely controlled hand movements when using a pen contribute extensively to the brain's connectivity patterns that promote learning.

Although the participants used digital pens for handwriting, the researchers said that the results are expected to be the same when using a real pen on paper.

Their findings demonstrate the need to give students the opportunity to use pens, rather than having them type during class, the researchers said.

Handwriting but not Typewriting Leads to Widespread Brain Connectivity: A High-Density EEG Study with Implications for the Classroom, Frontiers in Psychology (2024). DOI: 10.3389/fpsyg.2023.1219945

Comment by Dr. Krishna Kumari Challa on January 27, 2024 at 11:28am

Stars travel more slowly at Milky Way's edge: Galaxy's core may contain less dark matter than previously estimated

By clocking the speed of stars throughout the Milky Way galaxy,  physicists have found that stars further out in the galactic disk are traveling more slowly than expected compared to stars that are closer to the galaxy's center. The findings raise a surprising possibility: The Milky Way's gravitational core may be lighter in mass, and contain less dark matter, than previously thought.

The new results are based on the researchers' analysis of data taken by the Gaia and APOGEE instruments. Gaia is an orbiting space telescope that tracks the precise location, distance, and motion of more than 1 billion stars throughout the Milky Way galaxy, while APOGEE is a ground-based survey.

The physicists analyzed Gaia's measurements of more than 33,000 stars, including some of the farthest stars in the galaxy, and determined each star's "circular velocity," or how fast a star is circling in the galactic disk, given the star's distance from the galaxy's center.

The scientists plotted each star's velocity against its distance to generate a rotation curve—a standard graph in astronomy that represents how fast matter rotates at a given distance from the center of a galaxy. The shape of this curve can give scientists an idea of how much visible and dark matter is distributed throughout a galaxy.

What they were really surprised to see was that this curve remained flat, flat, flat out to a certain distance, and then it started tanking. This means the outer stars are rotating a little slower than expected, which is a very surprising result.

The team translated the new rotation curve into a distribution of dark matter that could explain the outer stars' slow-down, and found the resulting map produced a lighter galactic core than expected. That is, the center of the Milky Way may be less dense, with less dark matter, than scientists have thought.

 Xiaowei Ou et al, The dark matter profile of the Milky Way inferred from its circular velocity curve, Monthly Notices of the Royal Astronomical Society (2024). DOI: 10.1093/mnras/stae034

Comment by Dr. Krishna Kumari Challa on January 26, 2024 at 8:49am

This "smart" material, called FG phase, is jelly-like and impenetrable for most macromolecules. It fills and blocks the nuclear pore channel. Importins and exportins, however, can pass through because their surfaces are optimized for sliding through an FG phase.

The cell's border control in the FG phase happens extremely fast—within milliseconds. Likewise, its transport capacity is enormous: A single nuclear pore can transfer up to 1,000 transporters per second through its channel. Even with such a high traffic density, the barrier of nuclear pores remains intact and keeps suppressing unwanted border crossings. HIV, however, subverts this control.
HIV packages its genome into a capsid. Recent evidence suggests that the genome stays inside the capsid until it reaches the nucleus, and thus also when passing the nuclear pore. But there is a size problem.
The central pore channel is 40 to 60 nanometers wide. The capsid has a width of about 60 nanometers and could just squeeze through the pore.

However, a normal cellular cargo would still be covered by a transporter layer that adds at least another ten nanometers. The HIV capsid would then be 70 nanometers wide—too big for a nuclear pore. Nevertheless, cryo-electron tomography has shown that the HIV capsid gets into the nuclear pore. But how this happens has been so far a mystery in HIV infection.

 Liran Fu et al, HIV-1 capsids enter the FG phase of nuclear pores like a transport receptor, Nature (2024). DOI: 10.1038/s41586-023-06966-w

Part 2

Comment by Dr. Krishna Kumari Challa on January 26, 2024 at 8:47am

How HIV smuggles its genetic material into the cell nucleus

Each year, about 1 million individuals worldwide become infected with HIV, the virus that causes AIDS. To replicate and spread the infection, the virus must smuggle its genetic material into the cell nucleus and integrate it into a chromosome.

Researchers have now discovered that its capsid has evolved into a molecular transporter. As such, it can directly breach a crucial barrier, which normally protects the cell nucleus against viral invaders. This way of smuggling keeps the viral genome invisible to anti-viral sensors in the cytoplasm. Their study is published in Nature. 

Forty years after the human immunodeficiency virus (HIV) was discovered as the cause of AIDS, we have therapies that effectively keep the pathogen under control, but there is still no cure. The virus infects certain immune cells and hijacks their genetic program in order to multiply and replicate its own genetic material. The infected cells then produce the next generation of viruses until they are finally destroyed. The immunodeficiency symptoms of AIDS result from the massive loss of immune cells that normally fight viruses and other pathogens.
To use the host cell's resources, HIV must smuggle its genetic material through cellular defense lines into the cell nucleus. The nucleus, however, is closely guarded. Its nuclear envelope prevents unwanted proteins or harmful viruses from entering the nucleus and macromolecules from an uncontrolled escape. Yet, selected proteins can pass because the barrier is not hermetically sealed.

Thousands of tiny nuclear pores in the nuclear envelope provide a passageway. They control these transport processes with the help of importins and exportins—molecular transporters that capture cargoes with valid molecular "passcodes" and deliver them through the nuclear pore channel. A "smart" material turns these pores into one of nature's most efficient sorting and transport machines.

Part 1

• ‹ Previous
• 1
• …
• 309
• 310
• 311
• 312
• 313
• …
• 1110
• Next ›
• Page