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Comment by Dr. Krishna Kumari Challa on October 19, 2023 at 7:09am

Simulating cold sensation without actual cooling

Our skin plays a key role in perceiving temperature and the surroundings. For instance, we perceive the chill of the outdoors when our cheeks blush with cold, and we sense the onset of spring when our skin warms up gradually.

However, getting exposed to the same stimuli repeatedly, makes us accustomed to the stimuli, making it challenging to sense new sensations. This process, known as "temperature acclimatization," can interfere with our ability to gauge temperature changes in a virtual reality (VR) environment while switching scenes.

In a new study, researchers have developed a non-contact technology for simulating a cold sensation that continually generates thermal experiences while maintaining nearly constant skin temperature. This innovative approach leverages human body's natural sensitivity to rapid temperature changes.

The technology employs a combination of cold air flow and a light source to instantly switch between a quick cold and a gentle warm stimulus, inducing a cold sensation while maintaining the skin temperature fluctuations close to zero. Evaluation results have demonstrated that this system can provide a virtual cold sensation without any actual change in temperature. Moreover, the researchers have succeeded in replicating a cold sensation of the same intensity as one would experience with continuous skin temperature changes.

This technology offers a novel perspective on simulating skin sensations without altering the body's physical state. 

Jiayi Xu et al, Integration of Independent Heat Transfer Mechanisms for Non-Contact Cold Sensation Presentation With Low Residual Heat, IEEE Transactions on Haptics (2023). DOI: 10.1109/TOH.2023.3324754

Comment by Dr. Krishna Kumari Challa on October 19, 2023 at 7:05am

Researchers discover one of the world's darkest rivers

When the researchers came upon the Ruki River, they were quite taken aback. The water in this river, a tributary of the mighty Congo River, is so dark that you literally can't see your hand in front of your face.

Comparisons with other major tropical rivers show that the Ruki may even be the blackest large blackwater river on Earth—it's certainly a lot darker than the famous Rio Negro in the Amazon. The reason the water is black is that it contains large amounts of dissolved organic material and hardly any sediment because of the river's low gradient. These carbon-rich substances are mostly washed into the river by the rain, which falls on dead jungle vegetation and leaches out organic compounds from the decomposing plant material. What's more, the river floods the forest in the rainy season. It can take weeks for the often waist-deep water to slowly retreat, during which time it leaches organic substances.

The Ruki is one of the most DOC-rich river systems in the world (dissolved organic carbon). DOC usually comes in the form of organic acids that increase the acidity of the river water. This stimulates the release of carbon dioxide (CO₂) as the acids dissolve carbonates present in the water.

Travis W. Drake et al, Hydrology drives export and composition of carbon in a pristine tropical river, Limnology and Oceanography (2023). DOI: 10.1002/lno.12436

Comment by Dr. Krishna Kumari Challa on October 19, 2023 at 6:55am

Previous attempts have tried to make super lenses using novel materials. However, most materials absorb too much light to make the super lens useful.

Now researchers overcame this by performing the superlens operation as a post-processing step on a computer, after the measurement itself. This produces a 'truthful' image of the object through the selective amplification of evanescent (or vanishing) light waves.

This method could be applied to determine moisture content in leaves with greater resolution, or be useful in advanced microfabrication techniques, such as non-destructive assessment of microchip integrity. And the method could even be used to reveal hidden layers in artwork, perhaps proving useful in uncovering art forgery or hidden works.

 Subwavelength terahertz imaging via virtual superlensing in the radiating near field, Nature Communications (2023). DOI: 10.1038/s41467-023-41949-5

Part 2

Comment by Dr. Krishna Kumari Challa on October 19, 2023 at 6:54am

Superlensing without a super lens: Physicists boost microscopes beyond limits

Ever since Antonie van Leeuwenhoek discovered the world of bacteria through a microscope in the late seventeenth century, humans have tried to look deeper into the world of the infinitesimally small.

There are, however, physical limits to how closely we can examine an object using traditional optical methods. This is known as the diffraction limit and is determined by the fact that light manifests as a wave. It means a focused image can never be smaller than half the wavelength of light used to observe an object.

Attempts to break this limit with "super lenses" have all hit the hurdles of extreme visual losses, making the lenses opaque. Now physicists  have shown a new pathway to achieve superlensing with minimal losses, breaking through the diffraction limit by a factor of nearly four times. The key to their success was to remove the super lens altogether.

The work should allow scientists to further improve super-resolution microscopy, the researchers say. It could advance imaging in fields as varied as cancer diagnostics, medical imaging, or archaeology and forensics.

Researchers have now developed a practical way to implement superlensing, without a super lens. To do this, they placed their light probe far away from the object and collected both high- and low-resolution information. By measuring further away, the probe doesn't interfere with the high-resolution data, a feature of previous methods.

Part 1

Comment by Dr. Krishna Kumari Challa on October 18, 2023 at 9:50am

Digitally creating 16 million colours by chemistry

The DNA double helix is composed of two DNA molecules whose sequences are complementary to each other. The stability of the duplex can be fine-tuned in the lab by controlling the amount and location of imperfect complementary sequences.

Fluorescent markers bound to one of the matching DNA strands make the duplex visible, and fluorescence intensity increases with increasing duplex stability. Now, researchers  succeeded in creating fluorescent duplexes that can generate any of 16 million colours—a work that surpasses the previous 256 colours limitation.

This very large palette can be used to "paint" with DNA and to accurately reproduce any digital image on a miniature 2D surface with 24-bit color depth.

Tadija Kekić et al, A Canvas of Spatially Arranged DNA Strands that Can Produce 24-bit Color Depth, Journal of the American Chemical Society (2023). DOI: 10.1021/jacs.3c06500

Comment by Dr. Krishna Kumari Challa on October 17, 2023 at 10:47am

The researchers found that the secondary magnet (which they call a floater) rotated in sync with the rotor magnet—they spun at the same speed. They also found that the axis of the rotor magnet spun with a slight tilt—a situation that would destabilize the two magnets if they were not spinning. To better understand what was happening, the researchers created a simulation that allowed them to more easily manipulate the two magnets and their behavior.

They found that the magnetic field of the rotor magnet exerted some amount of torque on the floater resulting in the two magnets rotating in sync due to a gyroscopic effect. But the floater resisted, if only slightly, which accounted for the parallel configuration that developed. They also found that there was a very small amount of misalignment of the polar axis of the rotor magnet relative to its magnetic field—the resulting attractive and repulsive forces balanced each other out, allowing the floater to be held in a steady position during levitation.

Joachim Marco Hermansen et al, Magnetic levitation by rotation, Physical Review Applied (2023). DOI: 10.1103/PhysRevApplied.20.044036. On arXiv: doi.org/10.48550/arXiv.2305.00812

Part 2

Comment by Dr. Krishna Kumari Challa on October 17, 2023 at 10:46am

Why a spinning magnet can cause a second magnet to levitate

A team of physicists has found the reason a spinning magnet can cause a secondary magnet to levitate without the need for stabilization. In their paper published in the journal Physical Review Applied, the group describes experiments they conducted to learn more about the phenomenon and what they learned from them.

Prior research and anecdotal evidence have shown that if two magnets with north poles facing one another are brought close together, they will repel one another. Such force has been used for applications such as levitating trains. But these applications must account for the inherent instability that arises when magnets repel each other. More recently, scientists have found that if one of the magnets is spun at high speed, a second magnet can be repelled without the need for stabilizing—it remains levitated even when the first magnet is moved around. In this new effort, the researchers have uncovered the reason for such behavior. To learn more about the phenomenon, the research team paired several different types of magnets and spun them at different speeds while recording the action with high-speed cameras and motion tracking software. In studying the resulting imagery, the team was able to uncover the reason for the behavior.

Part 1

Comment by Dr. Krishna Kumari Challa on October 17, 2023 at 8:26am

The universe generates novel combinations of atoms, molecules, cells, etc. Those combinations that are stable and can go on to engender even more novelty will continue to evolve. This is what makes life the most striking example of evolution, but evolution is everywhere."

Among many implications, the paper offers:

1. Understanding into how differing systems possess varying degrees to which they can continue to evolve. "Potential complexity" or "future complexity" have been proposed as metrics of how much more complex an evolving system might become
2. Insights into how the rate of evolution of some systems can be influenced artificially. The notion of functional information suggests that the rate of evolution in a system might be increased in at least three ways: (1) by increasing the number and/or diversity of interacting agents, (2) by increasing the number of different configurations of the system; and/or (3) by enhancing the selective pressure on the system (for example, in chemical systems by more frequent cycles of heating/cooling or wetting/drying).
3. A deeper understanding of generative forces behind the creation and existence of complex phenomena in the universe, and the role of information in describing them
4. An understanding of life in the context of other complex evolving systems. Life shares certain conceptual equivalencies with other complex evolving systems, but the authors point to a future research direction, asking if there is something distinct about how life processes information on functionality (see also https://royalsocietypublishing.org/doi/10.1098/rsif.2022.0810).
5. Aiding the search for life elsewhere: if there is a demarcation between life and non-life that has to do with selection for function, can we identify the "rules of life" that allow us to discriminate that biotic dividing line in astrobiological investigations? (See also "Did Life Exist on Mars? Other Planets? With AI's Help, We May Know ...")
6. At a time when evolving AI systems are an increasing concern, a predictive law of information that characterizes how both natural and symbolic systems evolve is especially welcome

Laws of nature—motion, gravity, electromagnetism, thermodynamics—etc. codify the general behavior of various macroscopic natural systems across space and time.

The "law of increasing functional information" complements the 2nd law of thermodynamics, which states that the entropy (disorder) of an isolated system increases over time (and heat always flows from hotter to colder objects).

On the roles of function and selection in evolving systems, Proceedings of the National Academy of Sciences (2023). DOI: 10.1073/pnas.2310223120. doi.org/10.1073/pnas.2310223120

Part 4

Comment by Dr. Krishna Kumari Challa on October 17, 2023 at 8:26am

Life's evolutionary history is rich with novelties—photosynthesis evolved when single cells learned to harness light energy, multicellular life  evolved when cells learned to cooperate, and species evolved thanks to advantageous new behaviors such as swimming, walking, flying, and thinking.

The same sort of evolution happens in the mineral kingdom. The earliest minerals represent particularly stable arrangements of atoms. Those primordial minerals provided foundations for the next generations of minerals, which participated in life's origins. The evolution of life and minerals are intertwined, as life uses minerals for shells, teeth, and bones.

Indeed, Earth's minerals, which began with about 20 at the dawn of our solar system, now number almost 6,000 known today thanks to ever more complex physical, chemical, and ultimately biological processes over 4.5 billion years.

In the case of stars, the paper notes that just two major elements—hydrogen and helium—formed the first stars shortly after the big bang. Those earliest stars used hydrogen and helium to make about 20 heavier chemical elements. And the next generation of stars built on that diversity to produce almost 100 more elements.

Part 3

Comment by Dr. Krishna Kumari Challa on October 17, 2023 at 8:24am

Regardless of whether the system is living or nonliving, when a novel configuration works well and function improves, evolution occurs.

The authors' "Law of Increasing Functional Information" states that the system will evolve "if many different configurations of the system undergo selection for one or more functions."

In the case of biology, Darwin equated function primarily with survival—the ability to live long enough to produce fertile offspring.

The new study expands that perspective, noting that at least three kinds of function occur in nature.

The most basic function is stability—stable arrangements of atoms or molecules are selected to continue. Also chosen to persist are dynamic systems with ongoing supplies of energy.

The third and most interesting function is "novelty"—the tendency of evolving systems to explore new configurations that sometimes lead to startling new behaviors or characteristics.

Part 2

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