# gst: apropos of 'strange states', the modulation of PdGa crystals from conventional to 'exotic' behaviors

<< In topological materials, electrons can display behavior that is fundamentally different from that in 'conventional' matter, and the magnitude of many such 'exotic' phenomena is directly proportional to an entity known as the Chern number. New experiments establish for the first time that the theoretically predicted maximum Chern number can be reached—and controlled—in a real material. >>

<<  in the topological semimetal palladium gallium (PdGa) one of the most common classifiers of topological phenomena, the Chern number, can reach the maximum value that is allowed in any metallic crystal. That this is possible in a real material has never been shown before. (..)  the team has established ways to control the sign of the Chern number, which might bring new opportunities for exploring, and exploiting, topological phenomena. >>

Cherned up to the maximum. Paul Scherrer Institute. Jul 9, 2020.

https://phys.org/news/2020-07-cherned-maximum.html   

<< Here, (AA) show that the chiral crystal palladium gallium (PdGa) displays multifold band crossings, which are connected by exactly four surface Fermi arcs, thus proving that they carry the maximal Chern number magnitude of 4. By comparing two enantiomers, (They) observe a reversal of their Fermi-arc velocities, which demonstrates that the handedness of chiral crystals can be used to control the sign of their Chern numbers. >>

Niels B. M. Schroter, Samuel Stolz, et al. Observation and control of maximal Chern numbers in a chiral topological semimetal.  Science. Vol. 369, Issue 6500, pp. 179-183. doi: 10.1126/ science.aaz3480. Jul 10, 2020.

https://science.sciencemag.org/content/369/6500/179    

Also

D.J. Thouless, F. D.M. Haldane, J. M.Kosterlitz  << opened the door on an unknown world where matter can assume strange states. >> Oct 4, 2016

https://www.nobelprize.org/prizes/physics/2016/press-release/

# life: perform very large flights without flapping (among Andean condors)

<< Andean condors, at 10kg or more, are among the world’s heaviest flying birds. Once birds get this big, the energetic costs of flapping are so high they instead rely on currents of rising air to travel long distances. >>

AA << results showed that on average, condors fly for three hours a day, but they flap for less than two minutes of this - just 1% of their flight time. One bird even flew for more than five hours without a single flap, covering 172km. Surprisingly, the amount they flapped hardly changed whether they were in the Andes or the steppe, or whether it was windy or not. >>

<< Nonetheless, even in weak thermal conditions, which may occur in winter, (their) results suggest condors may flap for only around two seconds per km. This remarkably low investment in flapping flight is on a par with albatrosses. In fact, albatrosses appear to flap more than condors – between (1% and 15% of their flight time outside take-off) >>

<< What is particularly striking about our findings is that all the birds we studied were immature. There was some suggestion that flight performance improved with age, but the demonstration that all birds flap so rarely shows that it is possible for even young condors to invest little energy in flying. >>

Emily Shepard. We tagged Andean condors to find out how huge birds fly without flapping. Jul 13, 2020. 

https://theconversation.com/we-tagged-andean-condors-to-find-out-how-huge-birds-fly-without-flapping-142472

H. J. Williams, E. L. C. Shepard, et al

 Physical limits of flight performance in the heaviest soaring bird.  PNAS. doi: 10.1073/ pnas.1907360117. Jul 13, 2020

https://www.pnas.org/content/early/2020/07/09/1907360117

# evol: iterative hacking mechanics; a large group of viruses can assemble human-virus codes to produce novel chimeric (UFO) proteins

<< Like a scene out of "Invasion of the Body Snatchers," a virus infects a host and converts it into a factory for making more copies of itself. Now researchers have shown that a large group of viruses, including the influenza viruses and other serious pathogens, steal genetic signals from their hosts to expand their own genomes. >>

AA << looked at a large group of viruses known as segmented negative-strand RNA viruses (sNSVs), which include widespread and serious pathogens of humans, domesticated animals and plants, including the influenza viruses and Lassa virus (..) by stealing genetic signals from their hosts, viruses can produce a wealth of previously undetected proteins. The researchers labeled them as UFO (Upstream Frankenstein Open reading frame) proteins, as they are encoded by stitching together the host and viral sequences. There was no knowledge of the existence of these kinds of proteins prior to this study. >>

Viruses can steal our genetic code to create new human-virus genes. The Mount Sinai Hospital. Jun 18, 2020.

https://phys.org/news/2020-06-viruses-genetic-code-human-virus-genes.html

Jessica Sook Yuin Ho, Matthew Angel, et al. Hybrid Gene Origination Creates Human-Virus Chimeric Proteins during Infection. Cell. Vol 181, Issue 7, P1502-1517.e23. doi: 10.1016/ j.cell.2020.05.035. June 25, 2020. 

https://www.cell.com/cell/fulltext/S0092-8674(20)30630-9

# gst: the physics of squeezing; how to squeeze out (quantum) noise

<< 'Squeezing' is used in physics, among other things, to improve the resolution of measuring instruments. It allows disturbing noise to be suppressed in a way that smaller signals can be detected more sensitively. (..) (AA) has now been able to show how such a squeezed state can be measured in a much simpler way than with the existing methods. Moreover, the new method allows examining squeezed states in systems where such measurements were not possible before. >> [1]

<< In the experiment (..) the thermal fluctuations of a vibrating nanomechanical string resonator are squeezed. The nanostring can be thought of as a tiny guitar string, a thousand times thinner and shorter than a human hair. (..)  If the string is deflected far enough, it ceases to behave linearly. This means that the force that deflects the string is no longer proportional to the force that pulls it back to its original position. The strong drive alters the thermal fluctuations as a result of a violation of the time reversal symmetry. In phase space, they no longer look like a circle but like an ellipse: At least in one direction, its diameter, i.e. the noise, becomes significantly smaller—it is squeezed. >> [1]

<< Quantum squeezing was a theory that was first proposed in the 1980s, the general idea being that quantum vacuum noise can be represented as a sphere of uncertainty along two main axes: phase and amplitude. If this sphere were squeezed, like a stress ball, in a way that constricted the sphere along the amplitude axis, this would in effect shrink the uncertainty in the amplitude state of a vacuum (the squeezed part of the stress ball), while increasing the uncertainty in the phase state (stress ball's displaced, distended portion). Since it is predominantly the phase uncertainty that contributes noise to LIGO, shrinking it could make the detector more sensitive to astrophysical signals. (..) The heart of the squeezer is an optical parametric oscillator, or OPO — a bowtie-shaped device that holds a small crystal within a configuration of mirrors. When the researchers direct a laser beam to the crystal, the crystal's atoms facilitate interactions between the laser and the quantum vacuum in a way that rearranges their properties of phase versus amplitude, creating a new, "squeezed" vacuum that then continues down each of the detector's arm as it normally would. This squeezed vacuum has smaller phase fluctuations than an ordinary vacuum, allowing scientists to better detect gravitational waves. >> [2]

[1] - Measure squeezing in a novel way. University of Konstanz. Jun 25, 2020.   https://phys.org/news/2020-06-measure-squeezing-in-a-novel.html ; 

J. S. Huber, G. Rastelli, et al. Spectral Evidence of Squeezing of a Weakly Damped Driven Nanomechanical Mode.  Phys. Rev. X 10, 021066 – Jun 23,  2020.   https://journals.aps.org/prx/abstract/10.1103/PhysRevX.10.021066 

[2] - Jennifer Chu. New instrument extends LIGO’s reach. Technology "squeezes" out quantum noise so more gravitational wave signals can be detected. MIT. Dec 5, 2019.   https://news.mit.edu/2019/ligo-reach-quantum-noise-wave-1205

# life: the transient floating entities suspended in the skies of Venus

<< From afar, Venus seems like the most uninhabitable planet of all. >>

<< NASA’s Magellan mission conducted radar mapping of the entire surface of Venus, penetrating its cloud layer and enabling (..) to reconstruct the first 3D map of the Venusian surface. >>

<< Beneath its carbon dioxide/nitrogen atmosphere, 90 times thicker than Earth’s, a hellscape of a surface awaits. >>

<< Although (..) successfully sent numerous landers, they’ve all failed after mere hours. The reason? A layer of sulfuric acid clouds enshrouds Venus at high altitudes. These radiation-reflecting clouds create a runaway greenhouse effect: responsible for Venus’s incredible temperatures. >>

<< At 60 kilometers (36 miles) in altitude, temperatures and atmospheric pressures are similar to Earth’s. The right ingredients for life, including carbon, oxygen, and nitrogen-rich molecules, are all abundant. Ultraviolet photos of Venus display "dark patches," which Harold Morowitz and Carl Sagan suggested could indicate microorganisms. >>

<< Above the cloud-tops, Venus has been called a "paradise planet." >>

Ethan Siegel. Yes, There Really Could Be Life In The Cloud Tops Of Venus. Jul 6, 2020. 

https://www.forbes.com/sites/startswithabang/2020/07/06/yes-there-really-could-be-life-in-the-cloud-tops-of-venus/   

Also: Magellan Mission to Venus

https://nssdc.gsfc.nasa.gov/planetary/magellan.html

# gst: 'transcriptional burst frequency' modulation (more or less noise) during gene regulation

<< In cells, genes are expressed through transcription, a process where genetic information encoded in DNA is copied into messenger RNA (mRNA). The mRNA is then translated to make protein molecules, the workhorses of cells. This entire process is subject to bursts of natural stochasticity—or randomness—which can impact the outcome of biological processes that proteins carry out. >>

<< This work for the first time identifies the role of randomness in altering the outcome of a developmental process.>> Madhav Mani. 

<< By analyzing experimental perturbations of Drosophila's senseless gene against mathematical models, the team determined the sources of the gene's stochasticity, and found that the randomness appears to be leveraged in order to accurately determine sensory neuron fates. >>

<< Let's say you are quickly flipping a light switch on and off, but you want more brightness out of your bulb. You could either get a brighter bulb that produced more photons per unit time, or you could leave the switch 'on' more than 'off,' (..) What we found is that organisms control the amount of gene expression by regulating how often the gene is permitted to switch on, rather than making more mRNAs when it is on. >> Madhav Mani. 

<< From these studies, we are learning rules for how genes can be made more or less noisy, (..) Sometimes cells want to harness the genetic noise—the level of variation in gene expression—to make randomized decisions. Other times cells want to suppress the noise because it makes cells too variable for the good of the organism. Intrinsic features of a gene can imbue them with more or less noise. >> Richard Carthew. 

Alex Gerage. Toward principles of gene regulation in multicellular systems. Northwestern University. Jul 1, 2020.

https://phys.org/news/2020-07-principles-gene-multicellular.html

Rachael Bakker, Madhav Mani, Richard W Carthew. The Wg and Dpp morphogens regulate gene expression by modulating the frequency of transcriptional bursts. eLife. doi: 10.7554/eLife.56076. Jun 22, 2020. 

https://elifesciences.org/articles/56076

# gst: contactless manipulation of droplets levitating in an acoustic wave

<< A unique, versatile, and material-independent approach to manipulate contactlessly and merge two chemically distinct droplets suspended in an acoustic levitator is reported. Large-amplitude axial oscillations are induced in the top droplet by low-frequency amplitude modulation of the ultrasonic carrier wave, which causes the top sample to merge with the sample in the pressure minimum below. The levitator is enclosed within a pressure-compatible process chamber to enable control of the environmental conditions. The merging technique permits precise control of the substances affecting the chemical reactions, the sample temperature, the volumes of the liquid reactants down to the picoliter range, and the mixing locations in space and time. >>

Stephen J. Brotton, Ralf I. Kaiser. 

Controlled Chemistry via Contactless Manipulation and Merging of Droplets in an Acoustic Levitator. Anal. Chem. 2020, 92, 12, 8371–8377. doi: 10.1021/ acs.analchem.0c00929. Jun 1, 2020. 

https://pubs.acs.org/doi/10.1021/acs.analchem.0c00929#

Levitating droplets allow scientists to perform 'touchless' chemical reactions.  American Chemical Society. Jun 24, 2020.

https://phys.org/news/2020-06-levitating-droplets-scientists-touchless-chemical.html