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Visualizzazione dei post in ordine di pertinenza per la query weak. Ordina per data Mostra tutti i post
Visualizzazione dei post in ordine di pertinenza per la query weak. Ordina per data Mostra tutti i post

sabato 2 gennaio 2021

# gst: the strong impact on nanosheets by the weak van der Waals force

<< Van der Waals is a weak force that allows neutral molecules to attract one another through randomly fluctuating dipoles, depending on distance. Though small, its effects can be seen in the macro world, like when geckos walk up walls. >> 

<< Van der Waals forces are everywhere and, essentially, at the nanoscale everything is sticky, (..) When you put a large, flat particle on a large, flat surface, there's a lot of contact, and it's enough to permanently deform a particle that's really thin and flexible. >> 
Matt Jones. 

<< the ubiquitous, "weak" van der Waals force was sufficient to indent a rigid silver nanosheet. The phenomenon suggests possible applications in nanoscale optics or catalytic systems. >>

<< In further experiments, (..) nanospheres could be used to control the shape of the deformation, from single ridges when two spheres are close, to saddle shapes or isolated bumps when the spheres are farther apart. >> 

Mike Williams. Weak force has strong impact on nanosheets. Rice University. Dec 15, 2020. 


Sarah M. Rehn, Theodor M. Gerrard-Anderson, et al. Mechanical Reshaping of Inorganic Nanostructures with Weak Nanoscale Forces. Nano Lett. doi: 10.1021/ acs.nanolett.0c03383. Dec 10, 2020. 


Also

keyword 'van der Waals' in FonT



lunedì 4 gennaio 2021

# gst: apropos of waves perturbed by weak turbulences

<< Wave phenomena are ubiquitous at all scales throughout the Universe, and where there are waves, there’s the potential for wave turbulence. Wave turbulence is the physical state that arises in a continuous medium when a large number of wave modes interact with each other randomly. >>

<< A specific case of wave turbulence in which weakly nonlinear waves propagate in an unbounded space is described by weak turbulence theory. Capturing the dynamics of this regime will be helpful to accurately model large fluid systems. >>

<< In a rotating fluid, the predicted wave spectrum for interacting weakly nonlinear inertial waves is perturbed by the formation of geostrophic modes—columnar vortices aligned with the rotation axis (..) (AA) successfully suppress geostrophic modes with the addition of two honeycomb-patterned plates, allowing them to confirm the predictions of weak turbulence theory. >>

Sergey Nazarenko. Verifying Weak Turbulence Theory.  Physics 13, 194. Dec 14, 2020. 


Eduardo Monsalve, Maxime Brunet, et al. Quantitative Experimental Observation of Weak Inertial-Wave Turbulence. Phys. Rev. Lett. 125, 254502. Dec 14, 2020.





mercoledì 9 settembre 2020

# gst: to reach detectability of a weak signal, they add background noise

<< In contrast to most sensors, for which noise is a problem that should be suppressed, (AA) found that adding just the right amount of background noise can actually increase a signal too weak for sensing by normal sensors, to a level that can reach detectability. >>

Walt Mills. To make a better sensor, just add noise. Pennsylvania State University. Sep 03, 2020. 


<< In this article, (AA) adopt a radical approach for next generation ultra-low-power sensor design by embracing the evolutionary success of animals with extraordinary sensory information processing capabilities that allow them to survive in extreme and resource constrained environments. Stochastic resonance (SR) is one of those astounding phenomena, where noise, which is considered detrimental for electronic circuits and communication systems, plays a constructive role in the detection of weak signals. >>

Akhil Dodda, Aaryan Oberoi, et al. 
Stochastic resonance in MoS2 photodetector. Nat Commun 11, 4406 (2020). doi: 10.1038/ s41467-020-18195-0. Sep 2, 2020.


Also 

keyword 'noise' in FonT


Also 

plus ambiguity and noise. Notes. Jul 06, 2007  (quasi-stochastic poetry)




sabato 13 maggio 2023

# gst: the robustness of a edge spiking.


<< Excitable media, ranging from bioelectric tissues and chemical oscillators to forest fires and competing populations, are nonlinear, spatially extended systems capable of spiking. Most investigations of excitable media consider situations where the amplifying and suppressing forces necessary for spiking coexist at every point in space. In this case, spiking requires a fine-tuned ratio between local amplification and suppression strengths. But, in Nature and engineered systems, these forces can be segregated in space, forming structures like interfaces and boundaries. Here, (AA) show how boundaries can generate and protect spiking if the reacting components can spread out: even arbitrarily weak diffusion can cause spiking at the edge between two non-excitable media. This edge spiking is a robust phenomenon that can occur even if the ratio between amplification and suppression does not allow spiking when the two sides are homogeneously mixed. >> ️

Colin Scheibner, Hillel Ori, et al. Spiking at the edge. arXiv:2304.06940v1 [cond-mat.soft]. Apr 14, 2023. 


Keywords: gst, excitable media, weak, spike, edge spiking  




lunedì 6 maggio 2024

# gst: random walk model for dual cascades in wave turbulence.

<< Dual cascades in turbulent systems with two conserved quadratic quantities famously arise in both two-dimensional hydrodynamic turbulence and also in wave turbulence based on four-wave interactions. >>

<< in wave turbulence the systematic spectral fluxes observed in a dual cascade do not require an irreversible dynamical mechanism, rather, they arise as the inevitable outcome of blind chance. >>️️

Oliver Bühler. Random walk model for dual cascades in wave turbulence. Phys. Rev. E 109, 055102. May 1, 2024. 

Also: waves, turbulence, random, weak, in https://www.inkgmr.net/kwrds.html 

Keywords: gst, waves, turbulence, weak turbulence, random, random walks


martedì 26 gennaio 2016

# s-gst-chem: weak long-range van der Waals interactions in self-assembly

<< The researchers found that weak long-range van der Waals (attractive or repulsive forces between molecules or atomic groups that do not arise from interactions due to a covalent bond or electrostatic force) yielded the largest contribution to the molecule-surface interaction >>

A self-assembling molecular nanoswitch
A possible future molecular memory device. January 18, 2016

http://www.kurzweilai.net/a-self-assembling-molecular-nanoswitch

<< We find that on both substrates, the adsorbate-substrate interaction is dominated by attractive van der Waals forces >>

Moritz Müller, Katharina Diller, et al. Interfacial charge rearrangement and intermolecular interactions: Density-functional theory study of free-base porphine adsorbed on Ag(111) and Cu(111). The Journal of Chemical Physics, 2016; 144 (2): 024701 DOI: 10.1063/1.4938259 (open access)

http://scitation.aip.org/content/aip/journal/jcp/144/2/10.1063/1.4938259

lunedì 27 dicembre 2021

# gst: reshaping Kuramoto model, when a collective dynamics becomes chaotic, with a surprisingly weak coupling.

<< The emergence of collective synchrony from an incoherent state is a phenomenon essentially described by the Kuramoto model (..) Collective synchronization is a phenomenon in which an ensemble of heterogeneous, self-sustained oscillatory units (commonly known as oscillators) spontaneously entrain their rhythms. This is a pervasive phenomenon observed in natural systems and man-made devices, covering a wide range of spatio-temporal scales, from cell aggregates to swarms of fireflies >>

<< However, this is only partly true, (..) Kuramoto’s perturbative phase-reduction approach is valid for weak coupling. Specifically, oscillator heterogeneity and interactions appear at zeroth and linear orders in the coupling constant, respectively. >> 

AA << have introduced the ‘enlarged Kuramoto model’; a population of phase oscillators in which three-body interactions enter in a perturbative way. Remarkably, this makes a world of difference, drastically reshaping the traditional Kuramoto scenario. The ‘enlarged Kuramoto model’ exhibits a variety of unsteady states, including collective chaos and hyperchaos. >>

Ivan Leon, Diego Pazo. Enlarged Kuramoto Model: Secondary Instability and Transition to Collective Chaos. arXiv: 2112.00176v1 [nlin.AO]. Nov 30, 2021.


Also

More on the three-body problem (695 families of collisionless orbits). FonT. Oct 16, 2017. 


Keywords: gst, behav, instability, Kuramoto model, three-body interactions, chaos, collective chaos, hyperchaos.

giovedì 28 marzo 2019

# gst geo: a model of a cascading, zig-zag fashion earthquake on weak crustal faults

<< The model confirmed that the Kaikoura earthquake involved a complex cascade of fault ruptures, which propagated in a zig-zag fashion. Propagation velocities along the individual fault systems were not unusually slow, but the complex geometry of the fault network and delays at the transitions between fault segments led to a tortuous rupture path.  >>

A surprising, cascading earthquake. Ludwig Maximilian University of Munich. Mar 20, 2019.

https://m.phys.org/news/2019-03-cascading-earthquake.html

<< the complex fault system operates at low apparent friction thanks to the combined effects of overpressurized fluids, low dynamic friction and stress concentrations induced by deep fault creep. >>

Thomas Ulrich, Alice-Agnes Gabriel, et al. Dynamic viability of the 2016 Mw 7.8 Kaikoura earthquake cascade on weak crustal faults. Nature Comm. volume 10, Article number: 1213 (2019) Mar 14

https://www.nature.com/articles/s41467-019-09125-w

martedì 17 aprile 2018

# brain: a new learning theory; the role of weak synapses

AA << demonstrate a new type of abundant cooperative nonlinear dynamics where learning is attributed solely to the nodes, instead of the network links which their number is significantly larger >>

<< The network dynamics is now counterintuitively governed by the weak links, which previously were assumed to be insignificant >>

Shira Sardi, Roni Vardi, et al. Adaptive nodes enrich nonlinear cooperative learning beyond traditional adaptation by links. Scientific Reports. 2018; 8 (5100). doi: 10.1038/s41598-018-23471-7. March 23, 2018.

https://www.nature.com/articles/s41598-018-23471-7

The brain learns completely differently than we’ve assumed, new learning theory says. New post-Hebb brain-learning model may lead to new brain treatments and breakthroughs in faster deep learning.  Mar 28, 2018.

http://www.kurzweilai.net/the-brain-learns-completely-differently-than-weve-assumed-new-learning-theory-says

lunedì 2 marzo 2020

# gst: continuous, (not intermittent, perpetual) tremors and slips ...

<< Applying deep learning to seismic data has revealed tremor and slip occur at all times—before and after known large-scale slow-slip earthquakes—rather than intermittently in discrete bursts, as previously believed. Even more surprisingly, the machine learning generalizes to other tectonic environments, including the San Andreas Fault. >>

Machine learning reveals earth tremor and slip occur continuously, not intermittently. Los Alamos National Laboratory.  Feb 27, 2020.

https://m.phys.org/news/2020-02-machine-reveals-earth-tremor-intermittently.html

<< Slow earthquakes cyclically load fault zones and have been observed preceding major earthquakes on continental faults as well as subduction zones. Slow earthquakes and associated tremor are common to most subduction zones, taking place downdip from the neighboring locked zone where megathrust earthquakes occur. In the clearest cases, tremor is observed in discrete bursts that are identified from multiple seismic stations. By training a convolutional neural network to recognize known tremor on a single station in Cascadia, we detect weak tremor preceding and following known larger slow earthquakes, the detection rate of these weak tremors approximates the slow slip rate at all times, and the same model is able to recognize tremor from different tectonic environments with no further training. >>

Bertrand Rouet-Leduc, Claudia Hulbert, et al. Probing Slow Earthquakes With Deep Learning. Geophysical Research Letters. Volume 47, Issue 4. doi: 10.1029/2019GL085870. Jan 23, 2020.

https://agupubs.onlinelibrary.wiley.com/doi/full/10.1029/2019GL085870


sabato 7 novembre 2020

# gst: apropos of nano vortices: the stabilization of skyrmions by weak higher-order exchange interactions

<< Tiny magnetic whirls that can occur in materials—so-called skyrmions— hold high promises for novel electronic devices or magnetic memory in which they are used as bits to store information. A fundamental prerequisite for any application is the stability of these magnetic whirls. >>

<< Previously, a standard model of the relevant magnetic interactions contributing to the (energy) barrier has been established. >>

<< one type of magnetic interactions has so far been overlooked. In the 1920s Werner Heisenberg could explain the occurrence of ferromagnetism by the quantum mechanical exchange interaction which results from the spin dependent "hopping" of electrons between two atoms. "If one considers the electron hopping between more atoms, higher-order exchange interactions occur," says Dr. Souvik Paul, (..). However, these interactions are much weaker than the pair-wise exchange proposed by Heisenberg and were thus neglected in the research on skyrmions. >>

<< Based on atomistic simulations and quantum mechanical calculations (..)  (AA) have now explained that these weak interactions (at a higher temperature than room temperature) can still provide a surprisingly large contribution to skyrmion stability. Especially the cyclic hopping over four atomic sites (..) influences the energy of the transition state extraordinarily strongly (..), where only a few atomic bar magnets are tilted against each other. Even stable antiskyrmions were found in the simulations which are advantageous for some future data storage concepts but typically decay too fast. >>

Julia Siek­mann. Scientists find a new mechanism for the stabilization of skyrmions. Kiel University. Sep 21, 2020.


Paul, S., Haldar, S., von Malottki, S. et al. Role of higher- order exchange interactions for skyrmion stability. Nat Commun 11, 4756. doi: 10.1038/ s41467-020-18473-x. Sep 21, 2020.





giovedì 21 dicembre 2017

# gst: a case of stabilization by weak noise

<< An elusive state of matter - quantum spin liquid - may actually be enhanced rather than suppressed by disorder as seen in a compound that contains praseodymium, zirconium, and oxygen (Pr2Zr2O7) >>

<< Disorder is generally thought to be detrimental to creating materials with unusual magnetism or other quantum phenomena. However, a team found that weak disorder surprisingly stabilizes a rare quantum state called a quantum spin liquid >>

Stirring up a quantum spin-liquid with disorder. Dec 13, 2017.

https://m.phys.org/news/2017-12-quantum-spin-liquid-disorder.html

J.-J. Wen, S. M. Koohpayeh, et al. Disordered Route to the Coulomb Quantum Spin Liquid: Random Transverse Fields on Spin Ice in Pr2Zr2O7. Phys. Rev. Lett. 2017; 118 (107206). doi: 10.1103/PhysRevLett.118.107206. Mar 8, 2017.

https://journals.aps.org/prl/abstract/10.1103/PhysRevLett.118.107206

sabato 22 aprile 2023

# gst: when droplets are capable of self-propulsion as if they were surfing on a self-generated wave.


<< active droplets can move autonomously or oscillate between confining walls (..). Those behaviors could provide a clue about how life emerged from inanimate material. >>️

<< in the past decades, it has become clear that weak physical interactions among biomolecules are a crucial part of the answer. Such interactions allow some molecules to stay together transiently while avoiding others, which can lead to the spontaneous formation of droplets whose composition differs from their surroundings. Although biochemist Alexander Oparin suggested such ideas a century ago (..), experimental corroboration arrived only recently >>️

<< The key contribution of Demarchi and his collaborators is to demonstrate that droplet drift can enhance the heterogeneity of substrate and product. The resulting positive feedback allows droplets to move continuously as if they were surfing on a self-generated wave. >>️

David Zwicker. Droplets Come to Life. Physics 16, 45. Mar 20, 2023. 

AA << find that condensates move toward the center of a confining domain when this feedback is weak. Above a feedback threshold, they exhibit self-propulsion, leading to oscillatory dynamics. Moreover, catalysis-driven enzyme fluxes can lead to interrupted coarsening, resulting in equidistant condensate positioning, and to condensate division. >>
Leonardo Demarchi, Andriy Goychuk, et al. Enzyme-Enriched Condensates Show Self-Propulsion, Positioning, and Coexistence. Phys. Rev. Lett. 130, 128401. Mar 20, 2023.

Also

'drop', 'droplet', 'droploid', 'transition' in 

Keywords: gst, drop, droplet, waves, transition, liquid-liquid phase transition, nonequilibrium systems




giovedì 8 luglio 2021

# gst: apropos of 'disordered interactions', localization and dissociation of bound states and mapping to chaotic billiards concerning two particles on a chain

AA << consider two particles hopping on a chain with a contact interaction between them. At strong interaction, there is a molecular bound state separated by a direct gap from a continuous band of atomic states. Introducing weak disorder in the interaction, the molecular state becomes Anderson localized (exponential localization of all energy eigenstates,). At stronger disorder, part of the molecular band delocalizes and dissociates due to its hybridization to the atomic band. (AA) characterize these different regimes by computing the density of states, the inverse participation ratio, the level-spacing statistics and the survival probability of an initially localized state.  >>️

<< The atomic band is best described as that of a rough billiard for a single particle on a square lattice that shows signatures of quantum chaos. In addition to typical ``chaotic states'', (AA) find states that are localized along only one direction. These ``separatrix states'' are more localized than chaotic states, and similar in this respect to scarred states, but their existence is due to the separatrix iso-energy line in the interaction-free dispersion relation, rather than to unstable periodic orbits. >> 

Hugo Perrin, Janos K. Asboth, et al.  Two particles on a chain with disordered interaction: Localization and dissociation of bound states and mapping to chaotic billiards. arXiv: 2106.09603v1. Jun 17, 2021. 



venerdì 6 dicembre 2024

# gst: anomalous oscillation modes of (superfluid) pendant droplets; horizontal translation on a flat surface, bouncing off at the corner and vertical oscillations at the edge.

<< Droplets should exhibit various dynamical phenomena when adhered to a surface; not all of them are realized in classical fluids. Visualization of superfluid  4^He (helium-4) pendant droplets revealed that the droplets were horizontally translated on a flat surface, bouncing off at the corner, known as the Noether mode that reflects the translation symmetry. >>️

<< The droplets exhibited another mode in vertical oscillations with high amplitude that included oscillation of the droplet edge. The oscillation period remained constant even as the droplets grew, exhibiting an anomalously weak size dependence. The high mobility of the droplet edges owing to the superfluidity was a crucial factor for the appearance of these anomalous modes. >>️

Keita Onodera, Ryuma Nagatomo, et al. Anomalous Oscillation Modes of Superfluid Pendant Droplets. Phys. Rev. Lett. 133, 216001. Nov 19, 2024.

Also: drop, droplet, droploid, transition, in https://www.inkgmr.net/kwrds.html 

Keywords: gst, drop, droplet, droploid, transition


martedì 24 settembre 2019

# gst: apropos of weak bonds, hydrophobic cohesion to stabilize the double helix of DNA

<< The main stabilizer of the DNA double helix is not the base-pair hydrogen bonds but coin-pile stacking of base pairs, whose hydrophobic cohesion, requiring abundant water, indirectly makes the DNA interior dry so that hydrogen bonds can exert full recognition power. (..) (AA) speculate that hydrophobic catalysis is a general phenomenon in DNA enzymes. >>

<< The forces that stabilize the DNA double helix are a prerequisite for the secure storage of genetic information but their modest strength is also necessary for the efficient processes of replication, transcription, recombination, and repair systems-wherein thermal fluctuations, or "breathing," play an important role >>

Bobo Feng, Robert P. Sosa, et al. Hydrophobic catalysis and a potential biological role of DNA unstacking induced by environment effects. PNAS.  116 (35) 17169-17174; Aug 27, 2019.  doi: 10.1073/ pnas.1909122116.    https://www.pnas.org/content/116/35/17169

DNA is held together by hydrophobic forces. Chalmers University of Technology. Sep 23, 2019.     https://m.phys.org/news/2019-09-dna-held-hydrophobic.html   

venerdì 26 luglio 2024

# gst: Resonancelike emergence of chaos in complex networks of damped-driven nonlinear systems.

AA << solve a critical outstanding problem in this multidisciplinary research field: the emergence and persistence of spatiotemporal chaos in complex networks of damped-driven nonlinear oscillators in the significant weak-coupling regime, while they exhibit regular behavior when uncoupled. >>

They << uncover and characterize the basic physical mechanisms concerning both heterogeneity-induced and impulse-induced emergence, enhancement, and suppression of chaos in starlike and scale-free networks of periodically driven, dissipative nonlinear oscillators. >>️

Ricardo Chacon, Pedro J. Martínez. Resonancelike emergence of chaos in complex networks of damped-driven nonlinear systems. Phys. Rev. E 110, 014209. Jul 19, 2024. 

Also: network, chaos, in https://www.inkgmr.net/kwrds.html 

Keywords: gst, network, resonance, chaos


mercoledì 28 ottobre 2020

# astro: the effect of Yarkovsky acceleration to direct the asteroid Apophis (towards us, hypothetically)

<< A University of Hawai Institute for Astronomy (IfA) astronomer has revealed critical new findings linked to a large asteroid expected to pass extremely close to Earth. Dave Tholen and collaborators have announced the detection of Yarkovsky acceleration on the near-Earth asteroid Apophis. This acceleration arises from an extremely weak force on an object due to non-uniform thermal radiation. This force is particularly important for the asteroid Apophis, as it affects the probability of an Earth impact in 2068. >>

Massive asteroid subject of new findings. Oct 26, 2020. 


"2068" –Massive Asteroid Apophis on Path for Earth Impact. Oct 27, 2020.


Also

il ciottolo Apophis. Notes. May 05, 2006 (quasi-stochastic poetry). 


A wicked list in the dino-killing range; waiting for new entries. FonT. Jun 29, 2017. 



A few hints of our presence. Notes. Oct 13, 2006 (quasi-stochastic poetry)





giovedì 9 maggio 2024

# gst: bubble phases sliding over periodically modulated substrates

AA << analyze a bubble-forming system composed of particles with competing long-range repulsive and short-range attractive interactions driven over a quasi-one-dimensional periodic substrate. >>️

They << find various pinned and sliding phases as a function of substrate strength and drive amplitude. When the substrate is weak, a pinned bubble phase appears that depins elastically into a sliding bubble lattice. For stronger substrates, (AA) find anisotropic bubbles, disordered bubbles, and stripe phases. Plastic depinning occurs via the hopping of individual particles from one bubble to the next in a pinned bubble lattice, and as the drive increases, there is a transition to a state where all of the bubbles are moving but are continuously shedding and absorbing individual particles. This is followed at high drives by a moving bubble lattice in which the particles can no longer escape their individual bubbles. >>️

<< When the bubbles shrink due to an increase in the attractive interaction term, they fit better inside the pinning troughs and become more strongly pinned, leading to a reentrant pinning phase. For weaker attractive terms, the size of the bubbles becomes greater than the width of the pinning troughs and the depinning becomes elastic with a reduced depinning threshold. >>
C. Reichhardt, C.J.O. Reichhardt. Sliding dynamics for bubble phases on periodic modulated substrates. Phys. Rev. Research 6, 023116. May 2, 2024.

Also: bubble, elastic, transition, in https://www.inkgmr.net/kwrds.html 

Keywords: gst, bubble, pinned bubble, elastic, transition




mercoledì 17 marzo 2021

# phys: trace the birth and evolution of a quasiparticle entity

<< The idea of quasiparticles was first introduced in the 1930s by physicist Lev Landau, who was trying to gain a better understanding of complex quantum systems. >>

<< Over the past decades, physicists worldwide have been trying to gain a better understanding of non-equilibrium dynamics in quantum many-body systems. Some studies investigated what are known as quasiparticles, disturbances or entities in physical systems that exhibit behavior similar to that of particles. >>

In this study AA << observed three distinct regimes of impurity evolution marked by dynamic transitions. These regimes then link initial few-body and later many-body physical dynamics. >>

Ingrid Fadelli. Observing the birth of a quasiparticle. Mar 11, 2021.


<<  These results offer a systematic picture of polaron formation from weak to strong impurity interactions. They reveal three distinct regimes of evolution with dynamical transitions that provide a link between few-body processes and many-body dynamics. Our measurements reveal universal dynamical behaviour in interacting many-body systems and demonstrate new pathways to study non-equilibrium quantum phenomena. >>

Magnus G. Skou, Thomas G. Skov, et al. Non-equilibrium quantum dynamics and formation of the Bose polaron. 
Nat. Phys. (2021). doi: 10.1038/ s41567-021-01184-5. Feb 25, 2021.


"three distinct regimes"