Ultraslow Motion Research Articles

Unperceivable motion mimicking hygroscopic geometric reshaping of pine cones.

The hygroscopic deformation of pine cones, featured by opening and closing their scales depending on the environmental humidity, is a well-known stimuli-responsive model system for artificial actuators. However, it has not been noted that the deformation of pine cones is an ultra-slow process. Here, we reveal that vascular bundles with unique parallelly arranged spring/square microtubular heterostructures dominate the hygroscopic movement, characterized as ultra-slow motion with the outer sclereids. The spring microtubes give a much larger hygroscopic deformation than that of the square microtubes along the longitudinal axis direction, which bends the vascular bundles and consequently drives the scales to move. The outer sclereids with good water retention enable the vascular-bundle-triggered deformation to proceed ultra-slowly. Drawing inspiration, we developed soft actuators enabling controllable yet unperceivable motion. The motion velocity is almost two orders of magnitude lower than that of the same-class actuators reported, which made the as-developed soft actuators applicable in camouflage and reconnaissance.

Creep Motion of Elastic Interfaces Driven in a Disordered Landscape

The thermally activated creep motion of an elastic interface weakly driven on a disordered landscape is one of the best examples of glassy universal dynamics. Its understanding has evolved over the past 30 years thanks to a fruitful interplay among elegant scaling arguments, sophisticated analytical calculations, efficient optimization algorithms, and creative experiments. In this article, starting from the pioneer arguments, we review the main theoretical and experimental results that lead to the current physical picture of the creep regime. In particular, we discuss recent works unveiling the collective nature of such ultraslow motion in terms of elementary activated events. We show that these events control the mean velocity of the interface and cluster into “creep avalanches” statistically similar to the deterministic avalanches observed at the depinning critical threshold. The associated spatiotemporal patterns of activated events have been recently observed in experiments with magnetic domain walls. The emergent physical picture is expected to be relevant for a large family of disordered systems presenting thermally activated dynamics.

Intermittent collective dynamics of domain walls in the creep regime

We study the ultra slow domain wall motion in ferromagnetic thin films driven by a weak magnetic field. Using time resolved magneto-optical Kerr effect microscopy, we access to the statistics of the intermittent thermally activated domain wall jumps between deep metastable states. Our observations are consistent with the existence of creep avalanches: roughly independent clusters with broad size and ignition waiting-time distributions, each one composed by a large number of spatio-temporally correlated thermally activated elementary events. Moreover, we evidence that the large scale geometry of domain walls is better described by depinning rather than equilibrium universal exponents.

A Quadrupole-Central-Transition 17O NMR Study of Nicotinamide: Experimental Evidence of Cross-Correlation between Second-Order Quadrupolar Interaction and Magnetic Shielding Anisotropy.

We have examined the 17O quadrupole-central-transition (QCT) NMR signal from [17O]nicotinamide (vitamin B3) dissolved in glycerol. Measurements were performed at five magnetic fields ranging from 9.4 to 35.2 T between 243 and 363 K. We found that, in the ultraslow motion regime, cross-correlation between the second-order quadrupole interaction and magnetic shielding anisotropy is an important contributor to the transverse relaxation process for the 17O QCT signal of [17O]nicotinamide. While such a cross-correlation effect has generally been predicted by relaxation theory, we report here the first experimental evidence for this phenomenon in solution-state NMR for quadrupolar nuclei. We have discussed the various factors that determine the ultimate resolution limit in QCT NMR spectroscopy. The present study also highlights the advantages of performing QCT NMR experiments at very high magnetic fields (e.g., 35.2 T).

Nuclear magnetic relaxation by the dipolar EMOR mechanism: Multi-spin systems.

In aqueous systems with immobilized macromolecules, including biological tissues, the longitudinal spin relaxation of water protons is primarily induced by exchange-mediated orientational randomization (EMOR) of intra- and intermolecular magnetic dipole-dipole couplings. Starting from the stochastic Liouville equation, we have previously developed a rigorous EMOR relaxation theory for dipole-coupled two-spin and three-spin systems. Here, we extend the stochastic Liouville theory to four-spin systems and use these exact results as a guide for constructing an approximate multi-spin theory, valid for spin systems of arbitrary size. This so-called generalized stochastic Redfield equation (GSRE) theory includes the effects of longitudinal-transverse cross-mode relaxation, which gives rise to an inverted step in the relaxation dispersion profile, and coherent spin mode transfer among solid-like spins, which may be regarded as generalized spin diffusion. The GSRE theory is compared to an existing theory, based on the extended Solomon equations, which does not incorporate these phenomena. Relaxation dispersion profiles are computed from the GSRE theory for systems of up to 16 protons, taken from protein crystal structures. These profiles span the range from the motional narrowing limit, where the coherent mode transfer plays a major role, to the ultra-slow motion limit, where the zero-field rate is closely related to the strong-collision limit of the dipolar relaxation rate. Although a quantitative analysis of experimental data is beyond the scope of this work, it is clear from the magnitude of the predicted relaxation rate and the shape of the relaxation dispersion profile that the dipolar EMOR mechanism is the principal cause of water-1H low-field longitudinal relaxation in aqueous systems of immobilized macromolecules, including soft biological tissues. The relaxation theory developed here therefore provides a basis for molecular-level interpretation of endogenous soft-tissue image contrast obtained by the emerging low-field magnetic resonance imaging techniques.

Observation of the Second-Order Quadrupolar Interaction as a Dominating NMR Relaxation Mechanism in Liquids: The Ultraslow Regime of Motion.

We report variable-temperature (VT) (17)O NMR spectra of [5-(17)O]-d-glucose in an aqueous solution and in glycerol at 14.1 and 21.1 T. The VT (17)O NMR data cover a wide range of motion for which the molecular rotational correlation time (τc) of glucose changes more than 5 orders of magnitude. The observed line width of the (17)O NMR signal for [5-(17)O]-d-glucose displays a maximum at ω0τc ≈ 1 and a minimum at ω0τc ≈ 150, where ω0 is the angular Larmor frequency of (17)O. Under the ultraslow motion condition (i.e., ω0τc > 150), the line width of the observed (17)O NMR signal increases drastically with τc, suggesting that the second-order quadrupolar interaction becomes the predominant relaxation mechanism. While this relaxation mechanism has long been predicted by theory, the current study reports the first experimental observation of such a phenomenon. The implications of this new relaxation mechanism on the spectral resolution limit in liquid-state NMR spectroscopy for half-integer spins are discussed.

Does ultra-slow diffusion survive in a three dimensional cylindrical comb?

We present an exact analytical result on ultra-slow diffusion by solving a Fokker–Planck equation, which describes anomalous transport in a three dimensional (3D) comb. This 3D cylindrical comb consists of a cylinder of discs of either infinite or finite radius, threaded on a backbone. It is shown that the ultra-slow particle spreading along the backbone is described by the mean squared displacement (MSD) of the order of ln (t). This phenomenon takes place only for normal two dimensional diffusion inside the infinite secondary branches (discs). When the secondary branches have finite boundaries, the ultra-slow motion is a transient process and the asymptotic behavior is normal diffusion. In another example, when anomalous diffusion takes place in the secondary branches, a destruction of ultra-slow (logarithmic) diffusion takes place as well. As the result, one observes “enhanced” subdiffusion with the MSD ∼t1−αln(t), where 0 < α < 1.

South Home Town: Film and the imaginary city

Abstract; In December 2014 Steve Hawley exhibited a video installation made with Tony Steyger called Stranger than Known; South Home Town. It was about Southampton, its identity, or lack of identity, in the 50th anniversary of it being granted the title of city. The article digs deeper into the way that film can depict the city and uncover its resonance in the unconscious. The great port had been made a city but where did that leave the Southampton of the imagination? The beautiful mediaeval buildings had been largely erased by the terrible bombings of World War II; the romance and drama of the flying boats of Imperial Airways, not to mention the Mayflower and Titanic, were about transit, about departures and fugue, the flight from the familiar, and not the city’s people who were left behind. If the city is not just a collection of buildings and streets and people but also a myth, then what is Southampton’s myth? Drawing from the city symphonies of the 1920s, and new modes of film depiction such as the drone camera and ultra slow motion, the article looks at how the imaginary city is shaped in the minds of transient passengers and those that remain behind. Keywords; city, film, myth, travel, technology, video art

Bridging onshore and offshore present‐day kinematics of central and eastern Mediterranean: Implications for crustal dynamics and mantle flow

We present a new kinematic and strain model of an area encompassing the Calabrian and Hellenic subduction zones, western Anatolia and the Balkans. Using Haines and Holt's (1993) method, we derive continuous velocity and strain rate fields by interpolating geodetic velocities, including recent GPS data in the Balkans. Relative motion between stable Eurasia and the western Aegean Sea is gradually accommodated by distributed N‐S extension from Southern Balkans to the Eastern Corinth Gulf, so that the westward propagation of the North Anatolian Fault (NAF) throughout continental Greece or Peloponnesus is not required. We thus propose that the NAF terminates in north Aegean and that N‐S extension localized in the Corinth Gulf and distributed in Southern Balkans is due to the retreat of the Hellenic slab. The motion of the Hyblean plateau, Apulia Peninsula, south Adriatic Sea, Ionian Basin and Sirte plain can be minimized by a single rigid rotation around a pole located in the Sirte plain, compatible with the opening the Pelagian rifts (2–2.5 mm/yr) and seismotectonics in Libya. We interpret the trenchward ultraslow motion of the Calabrian arc (2–2.5 mm/yr) as pure collapse, the Calabrian subduction being now inactive. In the absolute plate motion reference frame, our modeled velocity field depicts two toroïdal crustal patterns located at both ends of the Hellenic subduction zone, clockwise in NW Greece and counter‐clockwise in western Anatolia. We suggest the NW Greece toroïdal pattern is the surface expression of a slab tear and consequent toroïdal asthenospheric flow.

Enjoy yourself

![][1]</img> For an instant it was exactly as it would happen in a film. The traffic that was thundering in my ears a few seconds ago was suddenly muffled as if it were miles away. My body felt cool and detached and everything appeared in ultra slow motion. The fraction of a second it took between jumping and hitting the deep water seemed stretched out like a long lazy summer afternoon. Looking back it was a stupid thing for a supposedly responsible doctor to be doing. I feel a bit guilty about admitting to it in a respected medical journal. I really should have known better. I'd just got carried away by the holiday atmosphere and joined a few other tourists copying some of the locals … [1]: /embed/graphic-1.gif

Free-space delay lines and resonances with ultraslow pulsed Bessel beams

We investigate the ultraslow motion of polychromatic Bessel beams in unbounded, nondispersive media. Control over the group velocity is exercised by means of the angular dispersion of pulsed Bessel beams of invariant transverse spatial frequency, which spontaneously emerge from near-field generators. Temporal dynamics in transients and resonances over homogeneous delay lines (dielectric slabs) are also examined.

Polymer interface changes in electrophoretic deposition

A Monte Carlo computer simulation model for the electrophoretic deposition of polymer chains on a discrete lattice is used to study the polymer density profile, interface growth, and its dependence on field, temperature, and molecular weight. The interface width ( W) decreases W∼ E −1/2 on increasing the field ( E). Width ( W) depends non-monotonically on the temperature ( T): a power-law decay is followed by a power-law increase on raising the temperature. Monotonic decay of the interface width with the molecular weight is possibly a stretched exponential. Conformation and dynamics of a tracer chain is used to probe its characteristics in interface to bulk region. The root mean square (rms) displacement of the center of mass of the tracer chain shows an ultra-slow motion, R∼ t ν ( ν∼0.1–0.01 at E=0.1–1.0) as the driven chain moves deeper from interface to bulk. Longitudinal compression of the radius of gyration ( R g) of the chain increases with the field; transverse components ( R g x , R g y ) are larger than the longitudinal component ( R g z ). The transverse component ( R g x ( y)) becomes oscillatory due to periodic squeezing at high fields as the field competes with the polymer barriers.

NMR Cross-Relaxation Study of Ultraslow Motion of the DomainWall in Channel Inclusion Compound

We report on an NMR study of ultraslow motions in the channel thiourea-hexachloroethane inclusion compound, [2.95(NH2)2CS] C2Cl6. Temperature dependent 1H NMR relaxation measurements of the powder thiourea-hexachloroethane at different resonance frequencies, from 23 to 55.5 MHz, have been carried out. Significant reduction of the spin-lattice relaxation time at 38 and 47 MHz is caused by the cross-relaxation of protons via the quadrupole chlorine nuclei. We show that the effective 1H-35Cl cross-relaxation observed in a powder sample is due to a slow mode process, when the molecules of the domain wall exhibit a correlated translational and rotational motion over the channel. Such propagation of the domain wall is confirmed by atom-atomic potential calculation. - Pacs: 76.60-k, 76.60.Es, 61.44.Fw, 61.66.Hq

Nuclear spin-lattice relaxation in the triply rotating frame and ultraslow molecular motions in solids

A method for measuring nuclear magnetic spin-lattice relaxation in solids in the effective field He3 acting in the triply rotating frame (TRF) is described. The method advances the previously described techniques whereby nuclear magnetic resonance and relaxation in the rotating (RF) and doubly rotating frames (DRF) are measured directly. In the present work, the RF and DRF are employed for suppressing the secular part of nuclear dipole-dipole (DD) interactions in the first two orders. As a result, the higher-order DD interactions (four- and five-particle ones) were separated, and their contribution to the nuclear spin-lattice relaxation in the TRF was studied experimentally. The experiments were carried out on protons in polycrystalline benzene. With the introduced technique, an overall spin-lattice relaxation decay in the TRF was recorded continuously during a single radio-frequency pulse with a length not exceeding 1 s. The contribution of multiproton nonsecular DD interactions to the proton spin-lattice relaxation in the TRF was observed selectively as a pronounced local minimum in the temperature dependence of the relaxation timeT 1ϱϱϱ. This contribution corresponds to ultraslow motion of benzene molecules with a rate about γHe3 ≈ 2π · (101-103) s-1 and is determined quantitatively by specific correlation functions corresponding to the multiparticle nonsecular DD interactions of protons. The prospects of using this method for studying ultraslow atomic and molecular dynamics in solids are discussed.

Ultraslow motion of domain wall in channel inclusion compound studied by means of NMR cross-relaxation

We report temperature dependent 1H NMR relaxation measurements of the powder thiourea-hexachloroethane inclusion compound, [2.95(NH 2) 2CS]·C 2Cl 6, at different resonance frequencies, from 23 to 55.5 MHz. Significant reduction of spin–lattice relaxation time at 38–47 MHz is caused by the cross-relaxation of protons via the quadrupole chlorine nuclei. We conclude that the effective 1H– 35Cl cross-relaxation observed in powder sample is due to a slow mode process, when the molecules of the domain wall exhibit a correlated translational and rotational motion over the channel. Such a propagation of the domain wall was predicted by atom-atomic potential calculation. We show that the NMR cross-relaxation effect is an effective tool in studying ultraslow motions, in particular in incommensurate structures.

The dynamic disorder of azulene: A single crystal deuterium nuclear magnetic resonance study

Deuterium nuclear magnetic resonance measurements on single crystals of azulene, specifically deuterated in the 1 and 3 positions, are reported. The quadrupole coupling tensor of these deuterons was determined by rotation experiments, yielding Qzz=182.2 kHz and η=0.056, with Qxx, the intermediate component (magnitude wise), oriented perpendicular to the molecular plane. The deuterium signals are inhomogeneously broadened and their widths are strongly anisotropic. This is quantitatively interpreted in terms of alignment disorder, induced by polar (up–down) disorder already known to be present in azulene from earlier x-ray measurements. It is shown that the alignment disorder is due to a planar distribution in the orientation of the molecules about the short axis, with a root mean square deviation of ±1°. The linewidths are strongly temperature dependent and reduce from about 8.9 kHz (maximum width) at room temperature to 1.6 kHz at 67 °C. This effect is interpreted in terms of molecular “up–down” flips, which average out both the polar and the alignment disorder. The rate of this process is found to be 104 s−1 at 40 °C, with an activation energy of 65 kJ/mol. Magnetization transfer experiments were performed by selectively inverting the magnetization of one of the deuterium doublets, followed by monitoring the subsequent approach to equilibrium of the whole spectrum. The results show the presence of additional dynamic processes in the ultraslow motion regime. These include molecular π flips about their long axes, as well as jumps between different sites in the lattice. The rate of both processes is about 0.084 s−1 at 57 °C. The intersite jumps are predominantly of the flip type, which interchange crystallographic symmetry related deuterons. From the rate of this process, a self-diffusion constant of 0.35×10−22 m2 s−1, at 57 °C, is estimated.

Reorientations in supercooled glycerol studied by two-dimensional time-domain deuteron nuclear magnetic resonance spectroscopy

The method of stimulated echoes was used to investigate the reorientational mechanism in the selectively deuterated glass-former glycerol, C3D5(OH)3 about 15 K above its calorimetric glass temperature. The reorientation process is fully isotropic. This enables an accurate determination of the decay constant, T1Q, of the quadrupolar spin order in the regime of ultraslow motion. The knowledge of this time constant has made it possible to reliably determine the rotational correlation function. The experimentally obtained evolution time-dependent correlation functions are compared with those from a simulation procedure involving a distribution of molecular jump angles. It is found that in glycerol small angles in the 2°–3° range dominate. They are accompanied by a small, but significant, fraction of larger jump angles.

Presidential Address: English Landed Society in the Twentieth Century III. Self-Help and Outdoor Relief

An ultra-slow motion serial whose episodes appear at intervals of twelve months needs a recapitulation of the story so far, however excellent the retentive capacity of scholars in comparison with soap opera audiences. The characters in question are the landowners, great and not so great, and the landed families who were already wellestablished on their estates and in their country houses in late Victorian Britain: and also the newcomers who have continued, throughout the twentieth century, to purchase landed estates and country houses. The main plot concerns the structure and distribution of landownership, and I have suggested that reports of the virtual disappearance of great estates in the last hundred years have been greatly exaggerated. There have been great changes, but while some individuals or entire families have fallen off the boat others have clambered aboard, so that in the 1990s perhaps one-third or more of the land of Britain is held in sizeable estates of 1,000 acres and upwards, compared with radier over one-half in the 1890s. The changing composition of the cast of landowners, and the wildly fluctuating fortunes of particular members of the cast, have fascinated many observers of the social and political scene, and these features provide the sub-plots. The undoubted decline of landed and aristocratic political and social predominance, leading to the virtual elimination of their influence on public life, and the equally undoubted decline, impoverishment, and extinction of some once great and famous landed families, have tended to become confused as cause and effect in some accounts.

Ultraslow motions and asymptotic lineshapes in ESR

The characteristic shape of the ESR spectra under ultraslow motion conditions, that is, when the rate of the rotational motion is much smaller than the magnetic anisotropies, is analyzed starting from the axial g-tensor problem with the diffusion model. By means of an effective relaxation frequency which takes into account both the intrinsic linewidth and the contribution of the dynamical processes, the asymptotic profiles and the corresponding scaling procedures of the spectrum are derived. By resorting to the adiabatic approximation the treatment is extended to radicals having axial hyperfine interactions, with the same asymptotic profiles predicting the shape of individual peaks in ultraslow motion spectra. The approximate spectrum calculated from the asymptotic lineshapes is compared with the numerical solution of the stochastic Liouville equation for a typical nitroxide radical. The early convergence of the outer peaks supports the use of their widths as probes of the correlation time and a simple procedure, which takes into account the correct scaling laws, is proposed for the analysis of experimental spectra. The model de[endence of the ultraslow motion spectra is also considered, with a comparison between the diffusion equation and the strong collision operator.

Search for ultra slow molecular motion in liquid crystals by spin thermometry

The existence of a slow dynamic mode, which relaxes the nuclear Zeeman energy at low fields, has been detected in liquid crystals by several nuclear magnetic resonance studies. To data, through, this slow mode has not been uniquely determined. The cross relaxation in the liquid crystal PAA and the dimer-exchange in the alkoxy-benzoic acid homologous series, interfere with the analysis of the low frequency relaxation. In p-(pentyl) phenyl- p-pentyloxy benzoate, which is not a dimer and cross relaxation between protons and other nuclei is not possible, the spin relaxation was analysed at low and high fields. By measuring T 1, T 1ρ, T 1D and applying spin thermometry, the existence of a slow mode was uniquely determined in this liquid crystal.