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Tuesday, 10 December 2019

The newly discovered Plastic hardens 1800 times on Heating

The soft, transparent gel at 25 ° C does not support weight (top), but quickly becomes rigid and opaque when heated to 60 ° C, becoming strong enough to support weight (bottom).

Heat hardening plastic

Researchers at Hokkaido University in Japan have developed a hydrogel that does the opposite of what polymer-based materials - such as plastic bottles - usually do: the material hardens when heated and softens when cooled.

The new material, which hardens 1,800 times when exposed to heat, could protect motorcyclists and race car drivers during accidents.

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Takayuki Nonoyama and his colleagues were inspired by how proteins remain stable within living things that survive in extreme heat environments, such as hot springs. Normally, heat "denatures" proteins, altering their structure and breaking their bonds. But proteins in thermophiles remain stable with heat, thanks to specially reinforced electrostatic interactions such as ionic bonds.

They mimicked this behavior by using a low-cost, non-toxic polyacrylic gel.

Phases of Polymers

The poly [acrylic acid] polyelectrolyte gel (PAAc) was immersed in an aqueous calcium acetate solution. PAAc itself behaves like any other polymer-based material, softening when heated. But when calcium acetate is added, the molecules of materials interact in a similar way to thermophilic proteins, causing PAAc to behave very differently.

As the temperature rises, the originally uniform gel separates into a dense polymer "phase" and a sparse polymer "phase." When it reaches a critical temperature of around 60 ° C, the dense phase undergoes severe dehydration, which strengthens ionic bonds and hydrophobic interactions between polymer molecules.

This causes the material to change rapidly from a soft, transparent hydrogel to a rigid, opaque plastic - 1,800 times stiffer, 80 times stronger and 20 times stronger than the original hydrogel.

Simply lowering the temperature causes the behavior to reverse, which opens up numerous possibilities for application.

Molecular structures and the mechanisms behind instant hydrogel thermal hardening.

Temperature sensitive intelligent materials

The team demonstrated one of the possible applications by combining the material with a fiberglass. The resulting composite fabric is soft at room temperature, but when it was rotated on an asphalt surface for five seconds at a speed of 80 km / hour, the heat generated by the friction was sufficient to harden the material with only minor abrasions. forming on the contact surface.

"Clothing made of similar fabric can be used to protect people during traffic accidents or sports, for example. Our material can also be used as a heat-absorbing window covering to keep indoors cooler," said Nonoyama.

"This polymeric gel can easily be made from versatile, inexpensive, non-toxic raw materials commonly found in everyday life. Specifically, polyacrylic acids are used in disposable diapers and calcium acetates are used in food additives. Our study contributes to basic research on new temperature sensitive polymers and applied research on intelligent temperature sensitive materials, "added Professor Jian Ping Gong.


Instant Thermal Switching from Soft Hydrogel to Rigid Plastics Inspired by Thermophile Proteins

Takayuki Nonoyama  Yong Woo Lee  Kumi Ota  Keigo Fujioka  Wei Hong  Jian Ping Gong

Advanced Materials 2019

A new type of artificial skin capable of self-regeneration

Research focused on the development of artificial skins could benefit both people with bioprostheses and robotics. In recent years, significant progress has been made in this direction, but none of the prototypes created to date have combined all the properties of human skin. This is today done. Recently, a team of Australian bioengineers has developed a new type of hydrogel that acts as an artificial skin and combines the strength, durability, flexibility and self-regeneration of human skin.

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This new hydrogel could be used as skin, tendon or muscle. " Thanks to the special chemistry we have incorporated into the hydrogel, it can repair itself after being damaged, as can human skin. Hydrogels are usually fragile, but our material is so strong that it could easily lift heavy objects. It can also change shape as human muscles do, "says chemist Luke Connal of the Australian National University.

The creation of a hydrogel that changes shape and has multiple functions has proven to be a permanent challenge for scientists, even with the natural inspiration of jellyfish, sea cucumbers and fly-flyers. While some hydrogels can withstand mechanical stresses, others have self-healing properties, and some have the ability to memorize shapes or change color.

An extremely reactive artificial skin

As far as UNA researchers know, no one else has been able to incorporate all these functions into one universal gel. By submitting their material to multiple tests, the authors claim to have created the first dynamic hydrogel that is solid, resistant to mechanical stresses, wear-resistant, self-healing and able to change shape and retain memory. The technical details have been published in the journal Advanced Materials.

Structure and preparation of the hydrogel. Credits: Zhen Jiang et al. 2019

Using this material, the researchers made extremely thin films of "flesh" without any breakage. When these films were heated or cooled, they then changed shape, bending one way or the other before returning to their original state with the right temperature.

Mechanical properties of the hydrogel: elasticity, strength, hardness. Credits: Zhen Jiang et al. 2019

Unlike many other hydrogels, which can sometimes take 10 minutes or more to change shape, this gel only takes 10 seconds to bend. Here, the key would be the dynamic hydrogen bonds of the gel and the imine (carbon-nitrogen) dynamic bonds, which work together to form "unprecedented properties".

Towards a more "human" robotics

Dynamic bonds have a high response to stimuli, making them perfect for environmental adaptation and self-healing, and imine bonds in particular have fast reaction kinetics that can allow rapid self-healing. . In addition, the authors claim that these materials can be easily prepared using simple chemistry, and if other polymers are added to the molecular mixture, perhaps even more functions can be achieved.

If the temperature is somehow used as a control, the authors think that this gel could one day be used as an artificial muscle. " In many sci-fi films, we see the most challenging work done by humanoid robots. Our research has taken an important step toward achieving this, "said materials engineer Zhen Jiang. In the meantime, the team hopes to turn their hydrogel into a printable 3D ink.


Tough, Self‐Healing Hydrogels Capable of Ultrafast Shape Changing

Zhen Jiang Broden Diggle India C. G. Shackleford Luke A. Connal

Volume31, Issue 48

Monday, 9 December 2019

The era of printed electronics is beginning

Large scale integrated circuit (LSI) prototypes straight out of the printer. [Image: Thor Balkhed]

Printed electronics

Swedish researchers say they have taken the missing step to bring electronic circuit printing from the laboratory to the factories, making it possible to apply organic electronics on a large scale.

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The decisive step was the integration between the new field of printed electronics and traditional silicon-based electronics manufactured by traditional mask and lithography techniques.

"This is a decisive step for a technology that was born at Linkoping University just over 17 years ago," said Professor Magnus Berggren.

"The advantage we have here is that we don't have to mix different manufacturing methods: Everything is done by screen printing and in relatively few processing steps. The key is to make sure the different layers finish in exactly the right place," added his colleague Peter Ersman.

Printing electronic circuits

Printing fully functional electronic circuits - they can be printed on flexible, transparent plastics or virtually any other material - has required a number of innovations over the past 17 years.

A first step was the creation of screen-printing screens that let you print extremely thin lines so that semiconductor inks can form components with precision and high density per area.

At least three additional challenges have since been faced: Reduce circuit size, increase quality so that the probability of all transistors in the circuit working is as close as possible to 100%, and - not least - integrating with the silicon-based circuits needed to process signals and communicate with the environment.

"One of the major advances is that we have been able to use printed circuits to interface with traditional silicon-based electronics. We have developed various types of printed circuits based on organic electrochemical transistors. One of them is the shift register, which can interface and handle contact between the silicon-based circuit and other electronic components such as sensors and displays. This means that we can now use a silicon chip with fewer contacts, which requires a smaller area and thus is much cheaper. , "said Berggren.

The internet of things will be the first major beneficiary of print electronics.

IoT and screens

The development of semiconductor inks was another decisive element for the miniaturization process and also for higher quality. "We can now place more than 1,000 organic electrochemical transistors on an A4 size plastic substrate and connect them in different ways to create different types of printed integrated circuits," said team member Professor Simone Fabiano.

These large-scale integrated circuits, or LSIs, can be used, for example, to power electrochromic screens themselves manufactured as printed electronics.

The big expectation, however, is that printed electronics will give the final push to make the low cost, low power circuits required by the internet of things.


Article: All-Printed Large-Scale Integrated Circuits Based on Organic Electrochemical Transistors
Authors: Peter Andersson Ersman, Roman Lassnig, Jan Strandberg, Deyu You, Vahid Keshmiri, Robert Forchheimer, Simone Fabiano, Goran Gustafsson, Magnus Berggren
Journal: Nature Communications
Vol .: 10, Article number: 5053
DOI: 10.1038 / s41467-019-13079-4

How do rats use empathy to prepare for danger?

Many studies have shown the tremendous abilities, individual or societal, of rats. They are able to solve basic puzzles, organize themselves into hierarchical colonies and perform complex tasks. They also manage to avoid danger in a particularly effective way. And researchers at the Netherlands Institute of Neuroscience have finally discovered a key element in this mechanism: empathy. Indeed, by recognizing and feeling the fear and emotions of their fellow creatures, rats know when to avoid an immediate danger.

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Their study shows that rats can use their siblings as antennas signaling danger, being extremely sensitive to the emotions of the rats that surround them. With this discovery, new targets for the treatment of empathic disorders in humans, such as psychopathy and frontotemporal dementia, could be identified in the future. The study was published in the journal PLOS Biology.

Preparing for danger through empathy

Contrary to the idea that empathy is one-way, where one person shares the pain of another, researchers have discovered a more interactive process in which animals align their emotions with mutual influences. They put two rats face to face, then surprised one of them (the demonstrator) with a brief electrical stimulation of the paws. They then observed the reaction of the two rats (the other being the viewer).

When a rat shows a reaction of fear, the other rat also feels it. In return, the reaction of the second conditions the fear felt by the first. Credits: Yingying Han et al. 2019

"The first thing we observed is that when you see your neighbor jump, the viewer is suddenly scared too. The viewer feels the fear of the demonstrator, "explains Rune Bruls. The spectator's reaction influences the way the demonstrator feels the shock. The spectators who were less afraid reduced the fear of their demonstrators. " The fear goes from one rat to another. In this way, a rat can prepare for danger before he even sees it . "

An empathic process similar to that of humans?

In humans, attending to the pain of others activates an area between the two hemispheres that is also active when we feel pain within our own body. This is considered one of the main areas of empathy of the brain. To see if this region is the same in the rat, the team injected a drug to temporarily reduce activity in this area.

"What we observed was striking: without the region that humans use to show empathy, the rats were no longer sensitive to the distress of another rat. Our sensitivity to other people's emotions may be more like that of the rat than many thought, "explains Keysers.

An empathy independent of the familiarity of individuals

The study also revealed that empathy is independent of whether or not to know the individual. For the rats that had never met, the emotions of the other rat were as contagious as for the rats that had shared the same "house" for 5 weeks. " It really challenges our notions about the origin of empathy, " explains Valeria Gazzola.

Familiarity between individuals does not influence the ability of rats to be empathic. They show empathy for both familiar and unknown individuals. Credits: Yingying Han et al. 2019

Many believe that humans and animals are empathic because they are sensitive to the suffering of their offspring. This parental concern then spreads to empathy for the closest friends. " What our data suggests is that an observer shares the emotions of others because it allows the observer to prepare for danger. It's not about helping the victim, but about avoiding becoming a victim yourself, "says Gazzola.

A level of empathy depending on past experiences

Although familiarity with the demonstrator plays no role in a rat's empathic or non-empathic reaction, previous experience does. Efe Soyman compared two groups of observers: one who had experienced electrical stimulation in the past and one who had not. He found that while experienced observers showed high levels of empathic fear, the inexperienced ones barely responded to what had happened to the demonstrator.

This is important because it shows that emotional contagion is not an innate mechanism, but something we must learn. " Rats are like humans: the more our experiences match those of the people we observe, the more we can understand how they feel, " Soyman concludes.


Bidirectional cingulate-dependent danger information transfer across rats

Yingying Han, Rune Bruls, Efe Soyman, Rajat Mani Thomas, Vasiliki Pentaraki, Naomi Jelinek, Mirjam Heinemans, Iege Bassez, Sam Verschooren, Illanah Pruis, Thijs Van Lierde, Nathaly Carrillo, Valeria Gazzola, Maria Carrillo, Christian Keysers

PLoS Biol 17(12): e3000524.


Sunday, 8 December 2019

Plants emit sounds when stressed

At first considered more or less inert by science, plants have in fact turned out to be very dynamic entities that can detect and interact with their environment as animals do. After showing that plants can communicate with each other using a universal chemical language, and even travel short distances, researchers have recently discovered that they are also capable of producing sounds in response to different types of stress.

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Although it has been revealed in recent years that plants are able to see, hear and smell, they are still considered silent. But, for the first time, they were recorded producing sounds when stressed, which researchers say could open a new field for precision farming, where farmers would listen to crops lacking water or nutrients.

Itzhak Khait and colleagues at Israel's Tel Aviv University discovered that tomato and tobacco plants emit sounds when they are stressed by lack of water or when their stems are cut off at frequencies that humans can not hear. Microphones placed 10 centimeters from the plants received sounds in the ultrasonic range of 20 to 100 kilohertz, which insects and some mammals would be able to hear and detect within 5 meters.

Researchers even suggest that butterflies may not lay their eggs on a plant that seems stressed by lack of water. Plants could even hear that others lack water, and react accordingly. Previously, devices were installed on plants to record the vibrations caused by the formation and explosion of air bubbles - a process known as cavitation - inside xylem tubes used for transporting 'water.

Sounds produced in response to different types of stress

But this new study is the first to record plant sounds emitted from a distance. On average, drought-stressed tomato plants emitted 35 sounds per hour, while tobacco plants produced 11. When plant stems were cut, tomato plants averaged 25 sounds per hour. and those of tobacco 15. Unstressed plants produced less than one noise per hour, on average.

a) Experimental protocol used by the researchers. b), c) and d): Amplitudes and number of sounds emitted by tobacco plants and tomatoes lacking water or cut. Credits: I. Khait et al. 2019

It is even possible to distinguish the sounds to know what is the source of the stress. Researchers conducted a deep-learning algorithm to distinguish between plant sounds and wind, rain, and other noise from the greenhouse, correctly identifying in most cases whether the stress was due to drought or at a break, depending on the intensity and frequency of the sound. Tobacco stressed by lack of water seems to produce louder sounds than cut tobacco, for example.

Depending on the frequency and intensity of the sounds emitted, it is possible to identify the plant species and the stress they experience. Credits: I. Khait et al. 2019

Although Khait and his colleagues are only interested in tomato and tobacco plants, they think that other plants can also make sounds when stressed. In a preliminary study, they also recorded ultrasonic sounds from a cactus ( Mammillaria spinosissima ) and amoxicillam ( Lamium amplexicaule ). Cavitation is a possible explanation of how plants generate sounds.

Better understanding plant stress: towards micro-controlled agriculture?

Enabling farmers to listen to water stressed plants could "open a new path in the field of precision agriculture," the researchers suggest. They add that such capacity will become increasingly important as climate change exposes more areas to drought.

The authors warn that the results can not yet be extended to other stresses, such as salt or temperature, as they do not lead to sounds. In addition, no experiment was conducted to show whether a butterfly or any other animal could hear and respond to the sounds emitted by the plants. This idea remains hypothetical, for the moment.

If plants emit sounds when stressed, cavitation is the most likely mechanism, says Edward Farmer of the University of Lausanne, Switzerland. But he is skeptical about the results and would like to see more controls, such as the sounds of a soil that dries without plants.

Note: This is Still an experimental research which yet needs to be published in valid journal, this article is taken from review Journal


Saturday, 7 December 2019

Quantum light processors are demonstrated in practice

Interlaced 3D light beams allow for quantum operations at room temperature and macro scale

Optical quantum processor

Two international teams, working separately, built prototypes of quantum processors made of light.

Qubits formed by intertwining laser beams are expected to make quantum computers less error prone and allow scalability, that is, scaling up processors to a large number of qubits.

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"While today's quantum processors are impressive, it's unclear whether today's designs can scale to extremely large sizes. Our approach starts with extreme scalability - built in from the start - because the processor, called a cluster state, is made of light. , "said Professor Nicolas Menicucci of RMIT University in Australia and leader of one of the teams.

A cluster state is a large collection of intertwined quantum components that perform quantum calculations when measured in a specific way - all operating at macroscopic scale using normal photonic components.

Both teams met the two fundamental requirements for cluster state operation, which comprise a minimum amount of qubits and quantum entanglement in the proper structure for their use in computational calculations.

To this end, specially designed crystals convert common laser light into a type of quantum light called compressed light , which is woven into a cluster state by a network of mirrors, light splitters, and optical fibers.

While the light compression levels achieved so far - which are a measure of photonic processor quality - are too low to solve practical problems, the design is compatible with approaches to achieving next-generation compression levels.

"Our experiment demonstrates that this design is workable - and scalable," said Professor Hidehiro Yonezawa of the University of New South Wales.

Animation showing the temporal evolution of the cluster state generation scheme

Quantum processor at room temperature

Mikkel Larsen and his colleagues at the Technical University of Denmark prefer to call his optical quantum processor prototype a "light carpet."

This is because, instead of the threads of an ordinary carpet, the processor is in fact a carefully crafted web of thousands of intertwined pulses of light.

"Unlike traditional cluster states, we use the temporal degree of freedom to achieve a two-dimensional interlaced network of 30,000 light pulses. The experimental setup is really surprisingly simple. Most of the effort has gone into developing the idea of ​​state generation. cluster, "said Larsen.

The Danish team has also been able to make its light carpet handle quantum entanglement at room temperature, noting that, in addition to error correction and simplification of technology, quantum optical processors can be cheaper and more powerful as they will allow the rapid increase in the number of qubits.

An optical quantum computer, therefore, does not require the expensive and complicated cooling technology used by superconducting qubits. At the same time, light-based qubits, which carry information in laser light, hold the information longer and can transmit it over long distances.

"By distributing the state of the cluster generated in space and time, an optical quantum computer can also scale more easily to contain hundreds of qubits. This makes it a potential candidate for the next generation of larger and more powerful quantum computers," reinforced Professor Ulrik Andersen.


Article: Generation of time-domain-multiplexed two-dimensional cluster state
Authors: Warit Asavanant, Yu Shiozawa, Shota Yokoyama, Baramee Charoensombutamon, Hiroki Emura, Rafael N. Alexander, Shuntaro Takeda, Jun-Ichi Yoshikawa, Nicolas C. Menicucci , Hidehiro Yonezawa, Akira Furusawa
Magazine: Science
Vol. 373-376
DOI: 10.1126 / science.aay2645

Article: Deterministic generation of a two-dimensional cluster state
Authors: Mikkel V. Larsen, Xueshi Guo, Casper R. Breum, Jonas S. Neergaard-Nielsen, Ulrik L. Andersen
Journal: Science
Vol. 366, Issue 6463, p. 369-372
DOI: 10.1126 / science.aay4354

Friday, 6 December 2019

Microgravity Brings New Hope For the Cancer Patients

Practical medical examinations of astronauts in recent years have revealed that space travel involves a number of health risks: osteoporosis, reduced lung volume, loss of muscle density, exposure to radiation, and so on. However, conversely, space can also bring unexpected therapeutic solutions. This is what biologists have discovered by observing that, immersed in microgravity, the cancer cells are unable to recognize and assemble, and eventually become neutralized.

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Since 2014, Joshua Choi, a biomedical engineering researcher at the University of Technology Sydney, has been studying the effects of microgravity on the physiology and cells of the human body. Early next year, he and his research team will visit the ISS to test a new method of treating cancer based on microgravity.

According to Chou, his research was inspired by a conversation he had with the late Stephen Hawking. During the conversation, Hawking noticed that nothing in the Universe defies gravity. Later, when a friend of Cabbage was diagnosed with cancer, he remembered what Hawking said and began to wonder, " What would happen to cancer cells if we removed them from gravity? ".

Cancer cells accustomed to evolve in a classical gravitational environment

In simple terms, cancer is a disease in which cells begin to divide uncontrollably and spread to certain parts of the body. Cancer cells do this by coming together to form a solid tumor in the body, which then develops until cells invade healthy tissues - such as the heart, lungs, brain, liver, pancreas, etc.

The process by which cancer develops and spreads would seem to indicate that there is a way in which cells are able to detect and gravitate together to form a tumor. However, researchers in biomedicine know that mechanical forces are the only way for cancer cells to detect each other, and that these forces have evolved to operate in a gravitational environment.

Immerse cancer cells in microgravity to block their evolution

This prompted Chou to think of ways in which the absence of gravity could prevent cancer cells from dividing and spreading. He and his team have tested the effects of microgravity on cancer cells in their laboratory. To do this, one of his students created a device that essentially consists of a container the size of a tissue box with a small centrifuge inside.

The researchers used a rotating arm centrifuge to recreate microgravity conditions. Credits: Sascha Kopp et al.

The cells of different cancers are contained in a series of tubes inside the centrifuge, which then rotates them until they experience the sensation of microgravity. As Chou said, the results have been rather encouraging. " Our work has shown that, in a microgravity environment, 80 to 90% of the cells of the four types of cancer tested - ovary, breast, nose and lung - were deactivated and then killed ."

a) Under the effect of microgravity, thyroid cancer cells are forced to rearrange their cytoskeleton. b) Culture of cancer cells under normal conditions; the cancerous tissue formed is dense. c) Cultivation of cancer cells in microgravity; the cancerous tissue formed is loose, porous and weakly bound. Credits: Sascha Kopp et al.

When subjected to microgravity conditions, the cancer cells were unable to detect themselves and therefore had a hard time getting together.

Towards in situ confirmation of results ... And the development of new cancer therapies

The next step, which will take place early next year, will be for the team to send their experience in the ISS aboard a space module specifically designed for this purpose (SpaceX will provide launch services). Chou and his colleagues will spend the duration of the experiment (seven days) in the field, where they will follow the progress of the experiment and will perform live cell imaging via data sources.

Joshua Chou, holding the experimental prototype that will be sent to the ISS next year. Credits: Sissy Reyes

Once the experiment is over, the cells will be frozen for their return trip to Earth. Chou and his colleagues will then examine them to look for genetic modifications. If the results on board the ISS confirm what Chou and his team discovered in the laboratory, he hopes they will be able to develop new treatments that can have the same effect as microgravity and neutralize the ability of cancer cells to to detect oneself.

Ideally, these treatments would not be a cure but could complement existing cancer treatment regimens. Combined with drugs and chemotherapy, treatments derived from this research would effectively slow the spread of cancer in the human body, making conventional treatments more effective and short-lived (and less expensive as well).


Researchers has developed the artificial brain cells

The chip in the center (the small green square) contains 120 artificial neurons. | University of Bath

The field of electronic circuits inspired by the brain has made a big leap forward. For the first time ever, researchers have been able to decode the complex behaviors of brain cells in order to recreate them in tiny computer chips. They demonstrated that a piece of silicon could behave exactly like a biological neuron.

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These tiny neurons may well change the way we design and build medical devices because they reproduce healthy biological activity, but only require one billionth of the energy needed by microprocessors.

It should be known that neurons behave in the same way as the electrical circuits of the body, but their behavior is less predictable, especially as regards the analysis of the relationship between their electrical input and output pulses. But these new artificial brain cells successfully mimic the behavior of rat neurons in two specific regions of the brain.

Professor Alain Nogaret (left) and research associate Kamal Abu Hassan (right) in the University of Bath laboratory. Credits: University of Bath

"Until now, the neurons looked like black boxes, but we managed to open them and examine the inside, " said Bath physicist Alain Nogaret. "  Our work is changing paradigms because it provides a robust method for reproducing the electrical properties of real neurons in great detail,  " he added.

For scientists, the ultimate goal is to use these neurons to design medical devices that are better adapted to patient needs, such as a smarter pacemaker, able to respond to new stressors and the demands of the person's heart. which essentially consists in improving the devices to better adapt them to the body.

Julian Paton, a physiologist at the Universities of Auckland and Bristol, said in his press release that recreating a biological activity was an interesting challenge because it "would offer tremendous opportunities for smarter medical devices that lead to personalized medicine approaches. for a range of diseases and disabilities.

In their work published in Nature Communications (see link below), researchers accurately reproduced the complete dynamics of hippocampal neurons and rat respiratory neurons.


Optimal solid state neurons

Kamal Abu-Hassan, Joseph D. Taylor, Paul G. Morris, Elisa Donati, Zuner A. Bortolotto, Giacomo Indiveri, Julian F. R. Paton & Alain

Nature Communications volume 10, Article number: 5309 (2019)

Thursday, 5 December 2019

Researchers identify the protein that controls the self-renewal of blood stem cells

Blood cells - red blood cells, white blood cells and platelets - are all initially derived from hematopoietic stem cells (HSCs). During hematopoiesis, these multipotent stem cells then differentiate into several progenitors that will give the final blood cells. In many blood disorders, bone marrow disorders can significantly reduce the production of HSC. But recently, researchers have discovered a protein mechanism that allows HSCs to self-renew, opening the door to new therapeutic solutions.

UCLA scientists have discovered a link between a protein and the ability of human blood stem cells to self-renew. In a study published in the journal Nature , the team reports that the activation of the protein causes the automatic renewal of blood stem cells at least twelve times under laboratory conditions.

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The multiplication of blood stem cells in conditions outside the human body could dramatically improve treatment options for blood cancers such as leukemia and for many inherited blood diseases. Blood stem cells, also known as hematopoietic stem cells, are found in the bone marrow where they are renewed and differentiated to create all types of blood cells.

Overcome rejection problems in bone marrow transplants

Bone marrow transplants have been used for decades to treat people suffering from certain diseases of the blood or immune system. However, they have significant limitations: it is not always possible to find a donor compatible with bone marrow, the immune system of the patient may reject foreign cells and the number of transplanted stem cells may not be sufficient to effectively treat disease.

In many blood diseases, bone marrow is reached, impacting the renewal of hematopoietic stem cells. Grafts are therefore performed, with risks of rejection generally high. Credits: Sophie Jacopin

When blood stem cells are removed from the bone marrow and placed in lab boxes, they quickly lose their ability to self-renew and they die or differentiate into other types of blood cells. Mikkola's goal of allowing the automatic renewal of blood stem cells under controlled laboratory conditions would open up many new possibilities for the treatment of many blood diseases, including the safer genetic engineering of blood stem cells. patients.

MLLT3: a gene involved in the renewal of blood stem cells

It could also allow scientists to produce blood stem cells from pluripotent stem cells, which can create any type of cell in the body. In the lab, researchers analyzed genes that go out when human blood stem cells lose their ability to self-renew, noting genes that are turned off when blood stem cells differentiate into specific blood cells, such as white or red blood cells.

They then placed the blood stem cells in lab boxes and observed which genes were inactivated. Using pluripotent stem cells, they made cells resembling blood stem cells that were unable to renew themselves and monitored which genes were not activated.

They found that the expression of a gene called MLLT3 was closely related to the potential for self-renewal of blood stem cells and that the protein generated by the MLLT3 gene gave the blood stem cells the necessary instructions to maintain its ability to self-renew. To do this, he collaborates with other regulatory proteins to ensure that important parts of the blood stem cell machinery remain operational during cell division.

A higher multiplication of HSCs thanks to the MLLT3 gene

The researchers wondered whether maintaining the level of MLLT3 protein in blood stem cells in lab boxes would be enough to improve their self-renewing abilities. Using a viral vector - a specially modified virus, capable of transmitting genetic information to the nucleus of a cell without causing disease - the team inserted an active gene MLLT3 into blood stem cells and observed that blood stem cells functional were able to multiply at least twelve times more.

The researchers found that activation of the MLLT3 (orange) gene allowed for greater turnover of hematopoietic stem cells. Credits: CurioCity

Other recent studies have identified small molecules - organic compounds often used to create pharmaceutical drugs - that help multiply stem cells from human blood in the laboratory. When Mikkola's team used these small molecules, she found that self-renewal of the blood stem cells generally improved, but that the cells could not maintain the appropriate MLLT3 levels and that they did not function properly. not as well when transplanted to mice.

Self-renewal of blood stem cells without side effects

Importantly, MLLT3 has allowed blood stem cells to self-renew at a reasonable pace; they have not acquired any dangerous characteristics such as excessive multiplication or mutation and the production of abnormal cells that can lead to leukemia.

The next steps for the researchers are to determine which proteins and which elements of the blood stem cell DNA influence the on-off switch for MLLT3, and how this can be controlled using the ingredients contained in the boxes. laboratory. With this information, they could eventually find ways to turn on and turn off MLLT3 without using a viral vector, which would be safer for use in a clinical setting.


MLLT3 governs human haematopoietic stem-cell self-renewal and engraftment

Vincenzo Calvanese, Andrew T. Nguyen, Hanna K. A. Mikkola

Nature (2019)

Wednesday, 4 December 2019

Chemists trigger the coldest chemical reaction ever

Chemical reactions are extremely fast processes, involving complex and successive molecular interactions. Until now, researchers could only observe the beginning and end phases of a chemical reaction, without being able to observe the course of the reaction itself. Recently, however, chemists at Harvard University have been able to cool molecules to such a low temperature that they have been slowed down to the point where researchers have the opportunity to observe the chemical reaction in detail. A feat that could pave the way for new technologies, from civil engineering to quantum computing.

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It's 500 nanokelvins, a few millionths of a degree above absolute zero. The icy nature of this configuration is important because at these temperatures, molecules tend to slow down to the point of almost stopping. For a chemical reaction to occur, slow molecules are usually not indicated.

But in this case, the reduction in temperature and speed gave the team led by Harvard University the opportunity to see something that had never been observed before: the moment when two molecules meet and form two new molecules. The results were published in the journal Science .

Slow down molecules to see their reaction in detail

The chemical reactions take only one picosecond, which makes it very difficult to observe what happens during this period of time. Even ultra-fast lasers acting as cameras can usually capture the beginning and the end of a reaction, but not what happens in the middle. Slowing the reaction through extremely cold temperatures obtained by the team was therefore the ideal solution.

The coldest temperature in the universe is absolute zero, a temperature that is experimentally impossible to reach. But it is possible to seriously approach it. Ultra-low temperatures mean very low energies, and therefore a much slower reaction: two rubidium potassium molecules chosen for their plasticity have been delayed during the reaction phase for a few microseconds.

Chemical reactions convert reagents into products via an intermediate state where bonds break and form. Often too short to be observed, this phase has so far escaped detailed observation. By "freezing" the rotation, the vibration and the movement of the reagents (here potassium-rubidium molecules) at a temperature of 500 nanokelvin (temperature barely higher than the temperature of absolute zero), the number of energetic states allowed for the products is limited. "Trapped" in the intermediate phase longer, researchers can then observe this phase directly with photoionization detection. Credits: Ming-Guang Hu

A technique known as photoionization detection was then used to observe what was happening between the two molecules, providing researchers with valuable real data to inform their models and assumptions. Being able to observe chemical reactions so closely and at such a fundamental level opens up the possibility of designing new reactions as well; an almost limitless number of combinations is imaginable, potentially useful in all areas, from material construction to quantum computing.


Direct observation of bimolecular reactions of ultracold KRb molecules

M.-G. Hu, Y. Liu, D. D. Grimes, Y.-W. Lin, A. H. Gheorghe2, R. Vexiau4, N. Bouloufa-Maafa4, O. Dulieu4, T. Rosenband2, K.-K. Ni,

Science  29 Nov 2019:
Vol. 366, Issue 6469, pp. 1111-1115
DOI: 10.1126/science.aay9531

If they exist, cosmic strings would be much harder to detect than expected

Following the Big Bang, the Universe has undergone several phase transitions that have resulted in broken symmetry of the physical laws. According to some cosmological models, some of these breaks in symmetry would have resulted in the formation of particular cosmic structures at the meeting point of unstable regions of the Universe; these structures are called topological defects, and cosmic strings are one of them. Cosmologists initially thought that signatures of these linear energy structures could be detected in the cosmic microwave background. However, recently, physicists have shown that these signatures would be too weak for their detection to be possible.

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Cosmic strings are hard to imagine, according to Oscar Hern谩ndez, a physicist at McGill University in Montreal. " Have you ever walked on a frozen lake? Have you noticed any cracks in the ice? It's still pretty solid, but cracked, "he says. These cracks are formed by a phase transition process similar to that of cosmic strings.

Topological defects predicted by physics beyond the Standard Model

Imperfect meeting points on the surface of a frozen lake form long cracks. In the structure where space and time intersect, they form cosmic strings, if the underlying physics is correct.

Researchers believe that in space, some fields determine the behavior of forces and fundamental particles. The first transition phases of the Universe gave birth to these fields. Today, these points of intersection between fields would appear as infinitely thin lines of energy across space.

Several simulations have shown, if they exist well, the distribution of the cosmic strings during the evolution of the Universe. These topological defects are provided by many theoretical models. Credits: Nature

Most physicists think that the standard model is incomplete. " Many extensions of the standard model naturally lead to cosmic strings after inflation. So, what we have is an object that is predicted by many models. Therefore, if they do not exist, all these models are excluded.

Cosmic strings: they would be impossible to detect in the cosmic microwave background

Hern谩ndez and Razvan Ciuca of Marianopolis College in Westmount, Quebec, had previously argued that a convolutional neural network - a powerful type of pattern search software - would be the best tool for locating string evidence in the CMB.

Assuming a perfect and noise-free CMB card, they wrote in a separate article in 2017, a computer using this type of neural network should be able to find cosmic strings even if their energy level (or "voltage") is remarkably low.

But in this new article published on the arXiv server , they showed that in reality, it is almost impossible to provide enough CMB data for the neural network to detect these potential strings. Other brighter microwave sources obscure the CMB and are difficult to disentangle completely. Even the best microwave instruments are imperfect, with limited resolution and random fluctuations in the accuracy of recording from one pixel to another.

They found that all these factors, and more, added to a level of information loss that no current or planned CMB recording and analysis method could ever overcome. This method of chase cosmic strings is a dead end. This does not mean that everything is lost, however.

A new method for detecting cosmic strings

A new method based on measurements of the expansion of the universe in all directions, in old parts of the Universe, could work. This method - called 21-centimeter intensity mapping - does not rely on the study of individual galaxy motions or on accurate CMB images.

Instead, it is based on measurements of the rate at which hydrogen atoms move away from the Earth, on average, in all parts of deep space. This method should be able to provide sufficiently constrained data to restart the hunt for cosmic strings.


Information Theoretic Bounds on Cosmic String Detection in CMB Maps with Noise
Razvan Ciuca1  Oscar F. Hern´andez1,2†

1Department of Physics, McGill University, 3600 rue University, Montr´eal, QC, H3A 2T8, Canada

2Marianopolis College, 4873 Westmount Ave.,Westmount, QC H3Y 1X9, Canada


Sperm whale found dead on Scottish coast with 100 kg of waste in stomach

With the rise of human industrial activities, ocean pollution has grown steadily in recent years, including plastic pollution whose signs are now visible in all oceans and seas of the world. The first victims of this situation are marine animals ingesting plastic waste. Many stranded marine mammals have, in recent years, been found with alarming amounts of objects in their stomachs. But recently, it is a new sinister record that has been established on the Scottish coast, where a sperm whale has been found with 100 kg of various waste in the stomach.

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The young sperm whale ( Physeter macrocephalus ) ran aground on November 28 at Luskentyre Beach, Scotland, in the Outer Hebrides Islands. He died shortly after. Fishing nets, ropes, tubes and an assortment of plastic wastes formed a compact mass inside the 20-tonne animal, and some appeared to have been there for some time.

The skin and fat of the whales isolating them so effectively, the bacteria inside a corpse of whale can multiply quickly, even when the temperature of the air is low. While bacteria help decompose leftovers, they produce gases that build up pressure inside the body, and the sperm whale on the Scottish beach was no exception.

After having naturally opened in two under the effect of internal gases, the sperm whale's body revealed 100 kg of various waste: ropes, nets, plastic bags, etc. Credits: SMASS

He "somehow exploded" during the examination of his corpse. " By the time we got near the corpse to look at it, the sperm whale had been dead for 48 hours and most of the guts were blown when we put a knife in, " writes a SMASS representative.

To better understand coastal strandings of marine animals

SMASS researchers and volunteers collect and analyze data on stranded animals along the Scottish coast, which includes 790 islands and stretches 19,000 kilometers. By performing necropsies and studying the remains of failed marine life - sharks, porpoises, dolphins, sea turtles and seals, as well as whales - scientists can better understand the biological and environmental conditions that lead to stranding.

While the amount of waste inside the whale was impressive, the animal appeared to be in good health and not malnourished. It is likely that the scoop of ball was a hindrance to digestion, but SMASS experts found no evidence that ingested debris was blocking the whale's intestines.

Plastic pollution: a deadly global danger for all marine animals

Other sinister examples of dead whales with belly full of plastic that have been stranded on the coasts of other countries exist. A pregnant sperm whale that floated on an Italian beach in April, died with 22 kg of waste in its stomach, and a Cuvier's beaked whale that arrived in the Philippines in March had swallowed 40 kg of waste. Sperm whales that were stranded in 2018 in Spain and Indonesia also had indigestible masses in their belly.

Large marine mammals are not the only ones to suffer from ocean pollution. Here is a photo of Emily Mirowski, a marine biologist at the Gumbo Limbo Center, performing the autopsy of a turtle. You can see the pile of plastic pieces extracted from his stomach next to it. Credits: Gumbo Limbo Nature Center

In the United Kingdom, stranded marine animal bodies usually have microplastic particles in their bodies, although it is unclear how this affects their overall health. But animals stranded with large amounts of debris in the belly are rare in the British coast. In the recent grounding, the garbage assortment in the whale's gut highlights the global problem of widespread marine pollution caused by various human activities.

Tuesday, 3 December 2019

Scientists have found a place on Earth where there is no life

Hyperacid, hypersalated and hot ponds in the geothermal field of Dallol (Ethiopia). Despite the presence of liquid water, this multi-extreme system does not allow the development of life, according to a new study. Credits: Puri L贸pez-Garc铆a

"WHY A PLANET WITH  LIQUID WATER IS NOT ENOUGH, Forms of life have been found everywhere: in Antarctica, at the bottom of the deepest mines and even in the alkaline waters of the so-called Dead Sea, micro-organisms of all kinds proliferate. But to Dallol, in the depression of Dancalia, in Ethiopia, nothing seems to survive, says research published in Nature Ecology & Evolution"

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A volcanic crater full of salt that gives off smoky toxic gases, where the water boils in intense hydrothermal activity and the daily temperatures in winter can exceed 45 ° C. A hostile and multi-extreme environment: very hot, very salty and very acidic at the same time. We have not just crossed the gates of hell: we are at  Dallol , in the  Danakil depression , in Ethiopia. It is in this place that a team of Franco-Spanish scientists, led by biologists  Jodie Belilla and  Purificaci贸n L贸pez-Garc铆a of the French Cnrs, has discovered how it is impossible for forms of life to remain.

A few months ago,  another study - also conducted in Dallol and published in  Scientific Reports - which highlighted an opposite result: the  finding of nanobacteria . That territory, so apparently inhospitable, was described as a valid example for understanding the environmental limits of life, both on Earth and in other parts of the Solar System. And the geothermal area of ​​Dallol was proposed as a terrestrial analogue of a primitive Mars (as it was three billion years ago). The conclusions of L贸pez-Garc铆a and colleagues, now published in  Nature Ecology & Evolution, are of a different opinion . "After analyzing many more samples than the previous jobs - with appropriate controls to avoid contaminating them and with a well calibrated methodology - we verified that in these salty, hot and hyperacid pools the microbial life is absent. As it is absent in the adjacent salt lakes, rich in magnesium », emphasizes L贸pez-Garc铆a.

Yes, there is a great variety of  halophilic archaea (primitive microorganisms that live in highly saline environments) in the desert and in the canyons around the hydrothermal site," adds the biologist, "but not in the hyperacid and hypersaline pools, nor in the so-called black and yellow lakes of Dallol, where magnesium abounds. And this despite the fact that the microbial dispersion, in this area, is intense, due to the wind and human visitors ".

There are two obstacles to life that prevent micro-organisms from developing inside the ponds: the abundance of magnesium salts  caotropic - capable of breaking hydrogen bonds and causing protein denaturation - and the simultaneous presence of conditions such as l hypersalinity, hyperacidity and high temperature.

To confirm this, the team of scientists has used various research methods such as: massive sequencing of  genetic markers to detect and classify microorganisms, chemical analysis of  brines and  scanning electron microscopy combined with  X-ray spectroscopy , used to analyze silicon-rich mineral precipitates. «In other studies, in addition to the possible contamination of samples with  archaea from adjacent lands, these mineral particles may have been interpreted as fossilized cells, but in reality they form spontaneously in brines even if there is no life, "observes L贸pez-Garc铆a, pointing out that caution is needed in relying on the apparently cellular appearance - or "biological" - of a structure, because it could be non-living systems.

Microbial cells (left) can be easily confused with silica-rich mineral precipitates (right). Credits: Karim Benzerara, Puri L贸pez-Garc铆a et al

"We would never expect to find life in similar environments on other planets, at least not life that is not based on a biochemistry similar to that on earth," says L贸pez-Garc铆a, insisting on the need to have more clues and analyze all possible alternatives before reaching a conclusion. "Our study shows that there are places on the earth's surface, such as the pools of Dallol, which are sterile even if they contain water in the liquid state," concludes the researcher, remarking as a criterion such as the presence of liquid water, often used to suggest the habitability of a planet, does not necessarily imply the presence of life.


Article: Hyperdiverse archaea near life limits at the geothermal polyextreme Dallol area

Authors: Jodie Belilla, David Moreira, Ludwig Jardillier, Guillaume Reboul, Karim Benzerara, Jose M. Lopez-Garcia, Paola Bertolino, Ana I. L贸pez-Archilla, Purification L贸pez-Garc铆a

Magazine: Nature Ecology & Evolution
Vol .: 3, pages 1552-1561

DOI: 10.1038 / s41559-019-1005-0

For the first time, the heartbeat of the blue whale has been recorded

With a length of up to 30 meters and a mass of up to 170 tonnes, the blue whale is currently considered to be the largest living animal and possibly the oldest living on Earth. To assume the physiological needs of such a template, the heart of the blue whale must be strong enough. Although marine biologists already knew that the animal's heart rate changes relatively quickly as it dives for food, they were surprised to find out how much. Indeed, during a dive, the heart of a blue whale goes from about 30 beats per minute to only 2.

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This is what a team of marine biologists discovered after recording for the first time the heartbeat of a blue whale. After placing a pulse monitor on a blue whale off the California coast, the researchers watched the gigantic creature sink and return to the surface for nearly 9 hours, alternately filling her lungs with air and her belly with hundreds of Pisces.

A heart with rapid variations to ensure physiological needs

During these deep foraging dives, the whale's heart rate changes abruptly, going up to 34 beats per minute at the surface and only two beats per minute in the deepest waters - which is about 30 at 50% slower than the researchers expected.

According to the new study published in PNAS , the mere fact of catching prey could push the heart of a blue whale into its physical limits - which could explain why no larger creature than the blue whale has ever been spotted on Earth.

" Animals that work at physiological extremes can help us understand the biological limits of size, " says Jeremy Goldbogen, a marine biologist at Stanford University. In other words: If the heart of a blue whale could not pump faster to feed its daily foraging expeditions, how could the heart of a larger animal pump even faster for more even bigger energy?

A slow heart rate during the dive

Blue whales are the largest animals ever to have lived on Earth. As adults, they can be more than 30 meters long, about the size of two school buses parked end-to-end. It takes a big heart to propel a creature of this size. The heart of a blue whale can weigh up to 180 kg (2015 failed specimen), about the size of a golf cart.

Scientists already knew that the pulse of a blue whale had to slow down deeply. When air-breathing mammals dive underwater, their bodies automatically begin to redistribute oxygen; the heart and brain receive more O2, while muscles, skin and other organs absorb less O2. This allows the animals to stay underwater longer with a single breath, resulting in a significantly lower heart rate than normal.

Graphs showing heartbeat variations of the blue whale as a function of depth and position of the animal. Credits: JA Goldbogen et al. 2019

This is true for humans as well as for blue whales. However, given the gigantic size of the whale and its ability to dive more than 300 meters deep, their hearts are pushed to limits far beyond ours. To find out exactly how much a blue whale's heart rate changes during a dive, the authors followed a group of whales they had previously studied in Monterey Bay, California, and fixed a special mounted sensor at the end of a 6 m pole on one of them.

A cardiac transition from 30 to 2 beats per minute

The studied whale was a male first sighted 15 years ago. The sensor was equipped with a plastic shell the size of a lunch box, equipped with four suction cups, two of which contain electrodes to measure the heart rate of the whale.

The researchers set the monitor on their first attempt, and he stayed there for 8½ hours when the whale dipped and resurfaced during dozens of foraging "missions".

Most of this time was spent underwater: the whale's longest dive lasted 16.5 minutes and reached a maximum depth of 184 m, while it never spent more than 4 minutes on the surface to fill the lungs. The sensor showed that, deep within each dive, the heart of the whale beat on average four to eight times per minute, with a minimum of two beats per minute.

Graphs showing the heart rate of the blue whale according to its lung volume and depth. Credits: JA Goldbogen et al. 2019

Between these low-tempo beats, the stretched aortic artery of the whale slowly contracted so that the oxygenated blood slowly moved into the body of the animal. Back on the surface, the whale's heart rate accelerated to 25 to 37 beats per minute, which quickly loaded the animal's bloodstream with enough oxygen to support the next deep dive.

The biggest heart on Earth

During these quick stopovers, the heart of the whale skirted its physical limits - it is unlikely that the heart of a whale could beat faster than that. This natural heart limit may explain why blue whales reach a certain size and why no known animal on Earth has ever been so tall.

Since a larger creature would need more oxygen to support its long, deep dive for food, his heart would need to beat even faster to get oxygen back to the surface. According to the authors of the study, this does not seem possible on the basis of current data.

Video presenting the work done by the researchers:


Extreme bradycardia and tachycardia in the world’s largest animal

ORCID ProfileJ. A. Goldbogen, ORCID ProfileD. E. Cade, J. Calambokidis, M. F. Czapanskiy, J. Fahlbusch, A. S. Friedlaender, W. T. Gough, S. R. Kahane-Rapport, M. S. Savoca, K. V. Ponganis, and P. J. Ponganis

PNAS first published November 25, 2019