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Comment by Dr. Krishna Kumari Challa on August 6, 2021 at 10:07am

Unsurprisingly, the theoretical speed limit for sending information in a quantum device (such as a quantum computer) depends on the device's underlying structure. The new protocol is designed for quantum devices where the basic building blocks—qubits—influence each other even when they aren't right next to each other. In particular, the team designed the protocol for qubits that have interactions that weaken as the distance between them grows. The new protocol works for a range of interactions that don't weaken too rapidly, which covers the interactions in many practical building blocks of quantum technologies, including nitrogen-vacancy centers, Rydberg atoms, polar molecules and trapped ions.

Crucially, the protocol can transfer information contained in an unknown quantum state to a distant qubit, an essential feature for achieving many of the advantages promised by quantum computers. This limits the way information can be transferred and rules out some direct approaches, like just creating a copy of the information at the new location. (That requires knowing the quantum state you are transferring.)

In the new protocol, data stored on one qubit is shared with its neighbors, using a phenomenon called quantum entanglement. Then, since all those qubits help carry the information, they work together to spread it to other sets of qubits. Because more qubits are involved, they transfer the information even more quickly.

This process can be repeated to keep generating larger blocks of qubits that pass the information faster and faster. So instead of the straightforward method of qubits passing information one by one like a basketball team passing the ball down the court, the qubits are more like snowflakes that combine into a larger and more rapidly rolling snowball at each step. And the bigger the snowball, the more flakes stick with each revolution.

But that's maybe where the similarities to snowballs end. Unlike a real snowball, the quantum collection can also unroll itself. The information is left on the distant qubit when the process runs in reverse, returning all the other qubits to their original states.

When the researchers analyzed the process, they found that the snowballing qubits speed along the information at the theoretical limits allowed by physics. Since the protocol reaches the previously proven limit, no future protocol should be able to surpass it.

part2

Comment by Dr. Krishna Kumari Challa on August 6, 2021 at 10:07am

New approach to information transfer reaches quantum speed limit

Researchers have  been investigating the theoretical constraints that will bound quantum technologies. One of the things researchers have discovered is that there are limits to how quickly quantum information can race across any quantum device.

These speed limits are called Lieb-Robinson bounds, and, for several years, some of the bounds have taunted researchers. For certain tasks, there was a gap between the best speeds allowed by theory and the speeds possible with the best algorithms anyone had designed. It's as though no car manufacturer could figure out how to make a model that reached the local highway limit.

But unlike speed limits on roadways, information speed limits can't be ignored when you're in a hurry—they are the inevitable results of the fundamental laws of physics. For any quantum task, there is a limit to how quickly interactions can make their influence felt (and thus transfer information) a certain distance away. The underlying rules define the best performance that is possible. In this way, information speed limits are more like the max score on an old school arcade game than traffic laws, and achieving the ultimate score is an alluring prize for scientists.

Now a team of researchers have found a quantum protocol that reaches the theoretical speed limits for certain quantum tasks. Their result provides new insight into designing optimal quantum algorithms and proves that there hasn't been a lower, undiscovered limit thwarting attempts to make better designs.

part1

Minh C. Tran et al, Optimal State Transfer and Entanglement Generation in Power-Law Interacting Systems, Physical Review X (2021). DOI: 10.1103/PhysRevX.11.031016

https://phys.org/news/2021-08-approach-quantum-limit.html?utm_sourc...

Comment by Dr. Krishna Kumari Challa on August 6, 2021 at 9:57am

Crop farmers face new disease pressures as climate changes
Climate change will increase the burden of crop diseases in some parts of the world and reduce it in others, new research suggests.
As the planet warms, the impact of crop diseases is likely to fall in tropical areas including Brazil, sub-Saharan Africa, India and Southeast Asia.

At higher latitudes (further from the equator), disease risk will grow—with Europe and China "particularly vulnerable".

The University of Exeter study, published in Nature Climate Change, says these changes will "closely track" variations in crop productivity expected under global warming.

Models suggest that rising temperatures will boost yields of most crops at high latitudes, while the tropics will see little or no gains.

The study also finds that the U.S., Europe and China are likely to see major changes in the mix of pathogens (diseases) affecting their crops.

"Rapid global dissemination by international trade and transport means pathogens are likely to reach all areas in which conditions are suitable for them."

Infection rates by plant pathogens are strongly determined by conditions including temperature.

Plant pathogen infection risk tracks global crop yields under climate change, Nature Climate Change (2021). DOI: 10.1038/s41558-021-01104-8 , www.nature.com/articles/s41558-021-01104-8

https://phys.org/news/2021-08-crop-farmers-disease-pressures-climat...

Comment by Dr. Krishna Kumari Challa on August 6, 2021 at 9:50am

New method opens the door to efficient genome writing in bacteria

Biological engineers have devised a new way to efficiently edit bacterial genomes and program memories into bacterial cells by rewriting their DNA. Using this approach, various forms of spatial and temporal information can be permanently stored for generations and retrieved by sequencing the cells' DNA.
The new DNA writing technique, which the researchers call HiSCRIBE, is much more efficient than previously developed systems for editing DNA in bacteria, which had a success rate of only about 1 in 10,000 cells per generation. In a new study, the researchers demonstrated that this approach could be used for storing memory of cellular interactions or spatial location.

This technique could also make it possible to selectively edit, activate, or silence genes in certain species of bacteria living in a natural community such as the human microbiome, the researchers say.

With this new DNA writing system, we can precisely and efficiently edit bacterial genomes without the need for any form of selection, within complex bacterial ecosystems.

This enables us to perform genome editing and DNA writing outside of laboratory settings, whether to engineer bacteria, optimize traits of interest in situ, or study evolutionary dynamics and interactions in the bacterial populations.

Efficient retroelement-mediated DNA writing in bacteria, Cell Systems (2021). DOI: 10.1016/j.cels.2021.07.001

https://phys.org/news/2021-08-method-door-efficient-genome-bacteria...

Comment by Dr. Krishna Kumari Challa on August 5, 2021 at 8:36am

Nearly 5 mn fewer girls to be born worldwide over next 10 years: study

An estimated 4.7 million fewer girls are expected to be born globally in the next 10 years because of sex-selective practices in countries with a cultural preference for male offspring, a trend that could undermine social cohesion in the long term, research showed on Tuesday. The research suggested that the projected shortfall in the number of girls being born will lead to a surplus of young men in around a third of the global population by 2030, which could lead to increased anti-social behaviour and violence. Sex-selective abortions have been on the rise for the past 40 years in countries throughout southeast Europe along with south and east Asia, with as-yet undetermined demographic impacts. To model what short- and long-term effect sex selection will have on societies, an international team of researchers analysed data from more than three billion births over the last 50 years. Focusing on 12 countries where the male-to-female ratio had increased since 1970 and another 17 where that ratio was at risk of increasing due to social or cultural trends, they simulated two scenarios.

The first assumed an increase in the rate of sex selection, based on statistical evidence.

The second scenario assumed increased sex selection in certain countries, based on observed trends and decreased fertility, but for which specific data were lacking.

In scenario 1, countries saw a shortfall of 4.7 million in the number of girls being born by 2030. For scenario 2, the figure jumped to more than 22 million globally by 2100.

Authors of the research, published in the BMJ medical journal, said the bias towards male offspring could lead to a "marriage squeeze" in affected countries.

"Fewer-than-expected females in a population could result in elevated levels of anti-social behaviour and violence, and may ultimately affect long-term stability and social sustainable development," they wrote.

The United Nations defines sex-selective practices alongside child marriage and female genital mutilation as harmful practices targeted under the Millennium Development Goals.

The authors of the new study called for better data collection of such practices in order to stamp them out, as well as wider education initiatives.

"A broader objective relates to the need to influence gender norms which lie at the core of harmful practices such as prenatal sex selection," they wrote.

"This calls for broader legal frameworks to ensure gender equality."

Source:  Agence France-Presse

Comment by Dr. Krishna Kumari Challa on August 5, 2021 at 8:24am

Together, the energy reaching Earth's surface from the sun and from the atmosphere is about 504 watts per square meter. Earth's surface emits about 79% of that back out. The remaining surface energy goes into evaporating water and warming the air, oceans and land.

The tiny residual between incoming sunshine and outgoing infrared is due to the accumulation of greenhouse gases like carbon dioxide in the air. These gases are transparent to sunlight but opaque to infrared rays—they absorb and emit a lot of infrared rays back down.

Earth's surface temperature must increase in response until the balance between incoming and outgoing radiation is restored.

Doubling of carbon dioxide would add 3.7 watts of heat to every square meter of the Earth. Imagine old-fashioned incandescent night lights spaced every 3 feet over the entire world, left on forever.

At the current rate of emissions, greenhouse gas levels would double from preindustrial levels by the middle of the century.

Climate scientists calculate that adding this much heat to the world would warm Earth's climate by about 5 degrees Fahrenheit (3 C). Preventing this would require replacing fossil fuel combustion, the leading source of greenhouse gas emissions, with other forms of energy.

https://theconversation.com/earths-energy-budget-is-out-of-balance-...

part 4

Comment by Dr. Krishna Kumari Challa on August 5, 2021 at 8:23am

Earth's Delicate Energy Balance

Comment by Dr. Krishna Kumari Challa on August 5, 2021 at 8:22am

Virtually all the energy in the Earth's climate system comes from the sun. Only a tiny fraction is conducted upward from the Earth's interior.

On average, the planet receives 340.4 watts of sunshine per square meter. All sunshine falls on the daytime side, and the numbers are much higher at local noon.

Of that 340.4 watts per square meter:
99.9 watts are reflected back into space by clouds, dust, snow and the Earth's surface.
The remaining 240.5 watts are absorbed—about a quarter by the atmosphere and the rest by the surface of the planet. This radiation is transformed into thermal energy within the Earth system. Almost all of this absorbed energy is matched by energy emitted back into space. A tiny residual—0.6 watts per square meter—accumulates as global warming. That may not sound like much, but it adds up.
The atmosphere absorbs a lot of energy and emits it as radiation both into space and back down to the planet's surface. In fact, Earth's surface gets almost twice as much radiation from the atmosphere as it does from direct sunshine. That's primarily because the sun heats the surface only during the day, while the warm atmosphere is up there 24/7.

part 2

Comment by Dr. Krishna Kumari Challa on August 5, 2021 at 8:21am

Earth's energy budget is out of balance – here's how it's warming the climate

Energy can neither be created nor destroyed. That's a fundamental property of the universe.

Energy can be transformed, however. When the sun's rays reach Earth, they are transformed into random motions of molecules that you feel as heat. At the same time, Earth and the atmosphere are sending radiation back into space. The balance between the incoming and outgoing energy is known as Earth's "energy budget."

Our climate is determined by these energy flows. When the amount of energy coming in is more than the energy going out, the planet warms up.

That can happen in a few ways, such as when sea ice that normally reflects solar radiation back into space disappears and the dark ocean absorbs that energy instead. It also happens when greenhouse gases build up in the atmosphere and trap some of the energy that otherwise would have radiated away.

part 1

Comment by Dr. Krishna Kumari Challa on August 5, 2021 at 7:46am

Study reveals how smell receptors work

All senses must reckon with the richness of the world, but nothing matches the challenge faced by the olfactory system that underlies our sense of smell. We need only three receptors in our eyes to sense all the colors of the rainbow—that's because different hues emerge as light-waves that vary across just one dimension, their frequency. The vibrant colorful world, however, pales in comparison to the complexity of the chemical world, with its many millions of odors, each composed of hundreds of molecules, all varying greatly in shape, size and properties. The smell of coffee, for instance, emerges from a combination of more than 200 chemical components, each of which are structurally diverse, and none of which actually smells like coffee on its own.

To form a basic understanding of odorant recognition we need to know how a single receptor can recognize multiple different chemicals, which is a key feature of how the olfactory system works 

The olfactory system has to recognize a vast number of molecules with only a few hundred odour receptors or even less. It's clear that it had to evolve a different kind of logic than other sensory systems.

In a new study researchers offer answers to the decades-old question of odour recognition by providing the first-ever molecular views of an olfactory receptor at work.

The findings, published in Nature, reveal that olfactory receptors indeed follow a logic rarely seen in other receptors of the nervous system. While most receptors are precisely shaped to pair with only a few select molecules in a lock-and-key fashion, most olfactory receptors each bind to a large number of different molecules. Their promiscuity in pairing with a variety of odors allows each receptor to respond to many chemical components. From there, the brain can figure out the odor by considering the activation pattern of combinations of receptors.

 The structural basis of odorant recognition in insect olfactory receptors, Nature (2021). DOI: 10.1038/s41586-021-03794-8 , www.nature.com/articles/s41586-021-03794-8

https://phys.org/news/2021-08-reveals-receptors.html?utm_source=nwl...

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