Rapid Motion Research Articles

Timing the break-up of the Baltica and Laurentia connection in Nuna – Rapid plate motion oscillation and plate tectonics in the Mesoproterozoic

Meso– to Neoproterozoic geological and paleomagnetic data support a direct connection between Baltica and Laurentia in both Nuna and Rodinia supercontinents, however in different relative configurations. Previous paleomagnetic data limit the time of break-up of Nuna core configuration and ca. 90° rotation of Baltica relative to Laurentia between 1.27 Ga and 0.99 Ga. Despite the well documented relative motion of continents, the tectonic mode during the Meso– to Neoproterozoic has been questioned and the operation of single lid tectonics at 1.6–1.0 Ga during the Nuna-Rodinia supercontinent cycles has been proposed.In this study, new paleomagnetic and whole rock 40Ar-39Ar geochronological data from a basic dyke in Stugun central Sweden are combined with coeval data to produce a 1.22 Ga (1.244–1.200 Ga) moderate-quality paleomagnetic pole. This is done to better estimate the break-up time of the core of Nuna and explore the plate tectonics at the Mesoproterozoic. The new pole fills part of the 1.247–1.140 Ga gap in the paleomagnetic record of Baltica. By comparing apparent polar wander paths (APWPs) and calculated drift velocities, a break-up of Baltica and Laurentia at 1.12–1.04 Ga is suggested. Plate velocities calculated for Laurentia, Baltica and Siberia for the time of the Nuna supercycle are similar and low to moderately high corresponding with the present-day tectonic speeds. Furthermore, the obtained velocity peaks may be related with onset of the break-up of the Nuna supercontinent, the break-up of the direct Baltica–Laurentia connection in Nuna and nascent Rodinia. We suggest that the velocity peaks and large oscillating shifts in late Mesoproterozoic pole positions for Laurentia and Baltica result from a combination of relative plate motion and inertial interchange true polar wander (IITPW) events. Both IITPW events and relative plate motions argue for an operation of plate tectonics in the Meso– to Neoproterozoic.

Oscillatory Motion of Water Droplets Both in Oil and on Superhydrophobic Surface under Corona Discharge.

Charged droplets driven by Coulomb force are an important part of a droplet-based micro reactor. In this study, we realized the rapid oscillatory motion of droplets both in oil and on superhydrophobic surface by injecting charges through corona discharge. Distinct from the oscillatory motion of water droplets under a DC electric field, charge injection can make the motion of water droplets more flexible. A droplet in the oil layer can move up and down regularly under the action of corona discharge, and the discharge voltage can control the movement period and height of the droplet. In addition, the left-right translation of droplets on a superhydrophobic surface can be achieved by injecting charges into the hydrophobic film surface through corona discharge. Two kinds of droplet motion behaviors are systematically analyzed, and the mechanism of droplet motion is explained. The present results could help establish new approaches to designing efficient machines in microfluidics and micromechanical equipment.

A novel spectrum handoff switching decision scheme for improved performance of secondary users in cognitive radio network

SummarySpectrum handoff (SH) in the cognitive radio network (CRN) is considered as a key challenging area to enhance the performance of secondary users (SUs) in CRN. If the primary user is detected, the SU may pause and stay on the same channel or may perform SH to another idle channel. An accurate and precise handoff decision improves the overall throughput and quality of experience of end‐users. In this paper, we introduce a new SH algorithm and continuous short‐sensing strategy to improve the overall throughput of SUs. In addition, we have derived the minimum length of the target channel sequence based on network‐specific parameters like desired call dropping probability. Further, an optimum channel search time is obtained to minimize the handoff delay. The simulation result shows that the proposed scheme improves the overall throughput of CRN, and the mean opinion score of different video applications increases by 10%, 4.6%, and 1% for rapid motion, gentle walk, and slight motion types of video applications. In the case of VoIP applications, the maximum simultaneous call is improved by 2 times in the case of G.711, 1.72 times in the case of G.729, and 1.66 times in the case of iLBC.

Influence of soil density on the solid-to-fluid phase transition in flowslide flume experiments

Flowslides are extremely hazardous due to their sudden failure and rapid flow-like motion. Focusing on the transient solid-to-fluid phase transition, we carried out a series of flume studies following various experimental scenarios, simultaneously recording granular velocity distributions, pore-water pressures, microseismicity, and acoustic emissions with precise time resolution (±0.01 s). The solid-to-fluid phase transition was recognized from the transition from solid-like shear deformation to flow-like velocity distribution. The variation in excess pore pressure in slopes during failure differed depending on initial soil state parameters, resulting in different failure patterns and distinct solid-to-fluid phase transition dynamics: (i) diffuse failure in loose slopes, the soil instability caused by increased local pore pressure (far from liquefaction) can trigger the whole failure of the slope; (ii) Mohr-coulomb failures in denser slopes, the soil mass slid along a localized shear zone, and progressively evolved to a diffuse shear throughout the slide mass. and (iii) retrogressive failures in very dense slopes. During the rapid motion process, the soil mass behaved as a fluid even after the excess pore pressure had dissipated, demonstrating that mechanisms other than soil liquefaction governed the fluid-like behavior. We inferred that the fluidization originated from the inherent shear-rate-dependent behavior of granular materials. Additional evidence for this hypothesis was provided by ultra-high frequency acoustic emissions (approximately 100 kHz) suggesting grain-scale collisions accompanying the fluidized runout.

Effects of Dynamical Degrees of Freedom on Magnetic Compass Sensitivity: A Comparison of Plant and Avian Cryptochromes.

The magnetic compass of migratory birds is thought to rely on a radical pair reaction inside the blue-light photoreceptor protein cryptochrome. The sensitivity of such a sensor to weak external magnetic fields is determined by a variety of magnetic interactions, including electron-nuclear hyperfine interactions. Here, we investigate the implications of thermal motion, focusing on fluctuations in the dihedral and librational angles of flavin adenine dinucleotide (FAD) and tryptophan (Trp) radicals in cryptochrome 4a from European robin (Erithacus rubecula, ErCry4a) and pigeon (Columba livia, ClCry4a) and cryptochrome 1 from the plant Arabidopsis thaliana (AtCry1). Molecular dynamics simulations and density functional theory-derived hyperfine interactions are used to calculate the quantum yield of radical pair recombination dependent on the direction of the geomagnetic field. This quantity and various dynamical parameters are compared for [FAD•- Trp•+] in ErCry4a, ClCry4a, and AtCry1, with TrpC or TrpD being the third and fourth components of the tryptophan triad/tetrad in the respective proteins. We find that (i) differences in the average dihedral angles in the radical pairs are small, (ii) the librational motions of TrpC•+ in the avian cryptochromes are appreciably smaller than in AtCry1, (iii) the rapid vibrational motions of the radicals leading to strong fluctuations in the hyperfine couplings affect the spin dynamics depending on the usage of instantaneous or time-averaged interactions. Future investigations of radical pair compass sensitivity should therefore not be based on single snapshots of the protein structure but should include the ensemble properties of the hyperfine interactions.

Vision: Neuronal mechanisms enabling stable perception

Eye movements cause rapid motion of the retinal image, potentially confusable with external motion. A recent study shows that neurons in mouse primary visual cortex distinguish self-generated from external motion by combining sensory input with saccade-related signals from the thalamic pulvinar nucleus.

Respiration-mediated self-switched triboelectric nanogenerator for wearable point-of-care prevention and alarm of asthma

To decrease the morbidity and mortality of asthma, prevention and acute episode alarms have become indispensable. The triboelectric nanogenerator (TENG)-based wearable point-of-care (POC) medical service presents a potential opportunity to implement round-the-clock prevention and continuously monitor the respiratory signals of asthmatic patients. Herein, a self-switched triboelectric nanogenerator (SS-TENG) mediated by respiratory motions is developed to provide prevention and emergency functions for asthma. The SS-TENG can supply sustained and stable electrical energy by smooth breathing motion to deliver preventive drugs with a transdermal system. This device is switched to a pulse mode by a strong and rapid respiratory motion. The outputs can be improved with orders of magnitudes, thereby endowing it with high sensitivity and resolution for emergency alarms of acute asthma episodes. Consequently, short-range visual and long-range wireless alarm indications are successfully demonstrated to send emergent messages to the monitoring terminals. As a wearable POC medical device, this SS-TENG may provide the preventive, diagnostic, and therapeutic services for respiratory diseases.

Preclinical MRI Using Hyperpolarized 129Xe

Although critical for development of novel therapies, understanding altered lung function in disease models is challenging because the transport and diffusion of gases over short distances, on which proper function relies, is not readily visualized. In this review we summarize progress introducing hyperpolarized 129Xe imaging as a method to follow these processes in vivo. The work is organized in sections highlighting methods to observe the gas replacement effects of breathing (Gas Dynamics during the Breathing Cycle) and gas diffusion throughout the parenchymal airspaces (3). We then describe the spectral signatures indicative of gas dissolution and uptake (4), and how these features can be used to follow the gas as it enters the tissue and capillary bed, is taken up by hemoglobin in the red blood cells (5), re-enters the gas phase prior to exhalation (6), or is carried via the vasculature to other organs and body structures (7). We conclude with a discussion of practical imaging and spectroscopy techniques that deliver quantifiable metrics despite the small size, rapid motion and decay of signal and coherence characteristic of the magnetically inhomogeneous lung in preclinical models (8).

Measuring material velocity and thickness mapping of flax fiber-reinforced plastic composites using automated ultrasonic rapid motion scanner

The interest in using sustainable materials was a part of the Sustainable Development Goals by the United Nations in 2015, its mission aims to eradicate poverty and conserve the environment by the year 2023. The use of engineered bio-fiber has the potential to replace the usage of synthetic fibers. However, the diversification of the application is limitless. The intended paper investigates the detection of impurities of cured pre-impregnated bio-composite using C-scan ultrasound. The Flax Fiber-Reinforced Plastic Composites were fabricated and cured with heat-assisted curing. The panels were inspected by an automatic ultrasonic rapid motion scanner to measure the material sound velocity of the Flax panel. As a result, the test obtained a reference value of Flax Fiber-Reinforced Plastic Composite material sound velocity of 3.17 (31700 mm/s) for thickness mapping. The obtain sound velocity value can be used as a future reference for inspecting any type of flax material specimen by using the rapid motion scanner from Eddyfi Technologies.

Combining beams in different locations for aerospace defense in a turbulent atmosphere

A fixed high-power laser system used as an aerospace defense weapon has limitations such as the transmitter size, serious thermal blooming during propagation, rapid motion, and the variation of the location of the target. In the present paper, we propose a method by arranging many high-power systems with adequate distance in a defense area. The intensity distribution and the energy irradiated on the target are studied and compared with a fixed laser system. Results show that adequate arrangement of many high-power laser systems can reply to the arbitrary and rapid motion of the target.

High intra-task and low inter-task correlations of motor skills in humans creates an individualized behavioural pattern

Our motor system allows us to generate an enormous breadth of voluntary actions, but it remains unclear whether and how much motor skill translates across tasks. For example, if an individual is good at gross motor control, are they also good at fine motor control? Previous research about the generalization across motor skills has been equivocal. Here, we compare human performance across five different motor skills. High correlation between task measures would suggest a certain level of underlying sensorimotor ability that dictates performance across all task types. Low correlation would suggest specificity in abilities across tasks. Performance on a reaching task, an object-hitting task, a bimanual coordination task, a rapid motion task and a target tracking task, was examined twice in a cohort of 25 healthy individuals. Across the cohort, we found relatively high correlations for different spatial and temporal parameters within a given task (16–53% of possible parameter pairs were significantly correlated, with significant r values ranging from 0.53 to 0.97) but relatively low correlations across different tasks (2.7–4.4% of possible parameter pairs were significantly correlated, with significant r values ranging from 0.53–0.71). We performed a cluster analysis across all individuals using 76 performance measures across all tasks for the two repeat testing sessions and demonstrated that repeat tests were commonly grouped together (16 of 25 pairs were grouped next to each other). These results highlight that individuals have different abilities across motor tasks, and that these patterns are consistent across time points.

Arcs on speedskating straightaways: forces, energy and angular momentum

The 10 000 m speedskating event during the 2022 winter Olympics brought a new world record at 12 min and 30.74 s. In a document released after the competitions, the gold medalist Nils van der Poel describes his technique, including a focus on horizontal forces and a rapid sideways motion in connection with stride changes on the straight sections of the track (the ‘straightaways’). Based on a video of the race, together with his written description, we suggest that van der Poel makes use of the properties of angular momentum to increase his speed during a stride by a rapid inwards shift of the centre of mass.

FastVOD-Net: A Real-Time and High-Accuracy Video Object Detector

Video object detection is a tough task due to the severe appearance degradation caused by rapid motion, sudden occlusion or rare poses. The great challenge facing video object detection is the simultaneous requirements on both accuracy and speed because the pursuit of one aspect usually causes significant expense to the other. Most existing methods mainly focus on improving detection accuracy with little attention to computationally efficient solutions, and thus they are impractical for many real-world applications. This motivates us to develop a real-time and high-accuracy video object detection method. In this paper, we propose a novel video object detector, called FastVOD-Net, which can yield highly accurate detection results at real-time speed. Specifically, we first develop a temporally-cascaded deformable alignment (TCDA) module to model the object displacements induced by video motion. Then, we introduce another two modules, namely spatially-refined temporal aggregation (SRTA) and attention-guided semantic distillation (AGSD), to improve the appearance feature of the currently processed frame and enhance the semantic representation of non-keyframes, respectively. For keyframe scheduling, we design an adaptive keyframe selection scheduler (AKSS) to adjust the keyframe interval online, making the keyframe usage more rational. On one hand, the characteristics of our FastVOD-Net enable it to sparsely perform expensive feature extraction, which significantly reduces the computational cost and thus guarantees real-time speed. On the other hand, the collaboration of the above tightly-coupled modules and adaptive keyframe scheduler makes FastVOD-Net fully exploit inter-frame temporal dependencies and thus guarantees high accuracy. Experiments on the ImageNet VID dataset show that our FastVOD-Net achieves 79.3% mAP at 29.6 fps or 81.2% mAP at 23.0 fps on an Nvidia RTX 2080 Ti GPU, which is the state-of-the-art performance in real time.

Rheological behavior and drying characteristics of ceria-based suspensions under various pH conditions

Microstructural changes in ceria-based suspensions at different pH values and corresponding rheological and drying properties were correlated. Ceria-based suspensions were classified into four zones based on their pH values. Well-dispersed or aggregated states of ceria particles in suspensions were mainly discerned by the magnitude of zeta-potential with pH variations and additional condensation reaction at relatively high pH. Suspensions with well-dispersed particles in a particular pH range exhibited transition between shear-thinning and Newtonian behavior along the shear rate and weak thixotropic features, whereas suspensions with agglomerated particles in different pH ranges showed significant shear-thinning and thixotropic behaviors with shear rate. The motion of particles within suspension droplets in each zone was quantified in terms of autocorrelation functions during drying using multi-speckle diffusing wave spectroscopy. Suspension droplets with well-dispersed particles showed conspicuous coffee-ring patterns compared to those with aggregated particles, owing to the rapid Brownian motion of well-dispersed particles. • The dispersion state of ceria particles depends on the pH condition. • A densely packed structure at high pH originates from the condensation reaction • Rheological properties and drying characteristics are correlated with the microstructures.

A well-posed multilayer model for granular avalanches: Comparisons with laboratory experiments

Granular avalanches are dangerous phenomena characterized by the rapid gravity-driven motion of granular solids. The complex dynamics of these flows can be effectively modeled by a multilayer approach, which, however, requires particular attention to the derivation of the model equations in order to allow stable solutions. In this work, we use a well-posed multilayer model, in which the μ(I)-rheology is employed and a dilatancy law, depending on the inertial number I, is also taken into account, and systematically compare it with various laboratory experiments. The model, whose well-posedness is guaranteed by a physically based viscous regularization, describes the evolution of a preset number of superimposed granular layers. As the sidewall friction is relevant under most experimental conditions, the model is fitted here with suitable resistance terms. Moreover, non-trivial closures for the mass exchanges are introduced to avoid any unrealistic partitioning of the flow domain during the avalanche evolution, and, hence, guarantee a regular spatial discretization along the normal to flow direction. The velocity fields are compared with different experiments in unsteady state, and comparisons of both velocity and volume fraction profiles are provided with steady uniform flow experiments. The results confirm the good capabilities of the multilayer model and the underlying μ(I)-rheology in capturing the granular flow dynamics. The experimental volume fraction profiles are qualitatively well reproduced by the proposed dilatancy law, while an overestimation is observed only in the upper, more dilute flow region with a thickness of a few grain diameters.

A Motor-Based Carbonaceous Nanocalabash Catalyst for Deep-Layered Bioorthogonal Chemistry.

Cu(I)-catalyzed azide-alkyne cycloaddition (CuAAC) reaction has been widely regarded as a promising avenue in bioorthogonal chemistry. The emerging heterogeneous copper catalysts have been developed with a series of exciting applications such as in situ activation of prodrugs because of their excellent stability and biocompatibility. However, due largely to the complex biophysical barriers in living organisms, most synthetic bioorthogonal drugs cannot penetrate deep pathological tissues. Especially in biofilm-associated infections, the biofilms severely block the penetration of traditional antimicrobial agents and increase the antibiotic resistance, which makes it extremely difficult to eliminate the biofilms. Inspired by self-propelled biological motors, such as enzymes, herein, we develop a NIR light-controllable carbonaceous nanocalabash (CNC) motor catalyst with good biocompatibility for active targeted synthesis of drugs inside the biofilms as a robust general-purpose bioorthogonal platform. Under the NIR laser, the CNC motor catalysts display a rapid autonomous motion and generate active molecules in the deep biofilm layers, removing the biofilms and eradicating the shielded bacteria. Our work will shed light on developing a robust bioorthogonal platform for active targeted synthesis of drugs in deep-layered living systems.

Pre-collapse motion of the February 2021 Chamoli rock–ice avalanche, Indian Himalaya

Abstract. Landslides are a major geohazard that cause thousands of fatalities every year. Despite their importance, identifying unstable slopes and forecasting collapses remains a major challenge. In this study, we use the 7 February 2021 Chamoli rock–ice avalanche as a data-rich example to investigate the potential of remotely sensed datasets for the assessment of slope stability. We investigate imagery over the 3 decades preceding collapse and assess the precursory signs exhibited by this slope prior to the catastrophic collapse. We evaluate monthly slope motion from 2015 to 2021 through feature tracking of high-resolution optical satellite imagery. We then combine these data with a time series of pre- and post-event digital elevation models (DEMs), which we use to evaluate elevation change over the same area. Both datasets show that the 26.9×106 m3 collapse block moved over 10 m horizontally and vertically in the 5 years preceding collapse, with particularly rapid motion occurring in the summers of 2017 and 2018. We propose that the collapse results from a combination of snow loading in a deep headwall crack and permafrost degradation in the heavily jointed bedrock. Despite observing a clear precursory signal, we find that the timing of the Chamoli rock–ice avalanche could likely not have been forecast from satellite data alone. Our results highlight the potential of remotely sensed imagery for assessing landslide hazard in remote areas, but that challenges remain for operational hazard monitoring.

Temporal evolution of mantle temperature and lithospheric thickness beneath the ∼1.1 Ga Midcontinent Rift, North America: Implications for rapid motion of Laurentia

The production of the magma volumes necessary for the formation of continental flood basalts is thought to result from extension-related decompression melting of thermo-chemically anomalous mantle. The relative importance of elevated mantle temperature or decompression associated with lithospheric thinning remains difficult to constrain because the temporal relationship between the initiation of extension and continental flood basalt is often ambiguous. The ∼1.1 Ga Midcontinent Rift (MCR) in North America provides an opportunity to probe these magma generation factors because the mantle thermo-chemical anomaly (Keweenaw plume) thought responsible for the continental flood basalts of the Keweenaw Large Igneous Province (LIP) intersected an existing rift. The role of elevated mantle temperatures in Keweenaw LIP magmatism remains ambiguous because a temporal decrease in MgO content in primitive lavas may reflect decreasing melting depths with time due to progressive lithospheric thinning, a temporal decrease in mantle temperature, or both. Furthermore, paleomagnetic studies show that Laurentia was moving rapidly during Keweenaw LIP magmatism, raising the question of how the plume remained connected to the MCR during 25 Myr of volcanism. Using samples from the most complete volcanic section preserved at Mamainse Point, Ontario, Canada, we constrain mantle potential temperature and lithospheric thickness by combining three major element thermobarometry models with forward modeling of rare earth element compositions. We find that the earliest stage of Keweenaw LIP magmatism (Early phase; 1109-1104 Ma) was governed by initially deeper melting (>85-100 km thick lithosphere) and high mantle potential temperatures (>1480-1630°C) related to the plume. Potential temperatures decreased to near-ambient conditions (∼1400-1445°C) during the latter portion of the Early phase, with these lower temperatures persisting throughout the Latent (1104-1098 Ma) and Main (1098-1090 Ma) phases. Major element-derived pressures of melt equilibration place broad constraints on lithospheric thickness, which decreased from ∼60-110 km at the onset of magmatism to 45-65 km by the Main phase. The decrease in primitive MgO contents thus reflects thinning lithosphere and decreasing mantle potential temperatures. We argue that the temporal decrease in mantle potential temperature reflects the severing of the connection between the MCR and Keweenaw plume after the Early phase of magmatism by the rapid plate motion. Our constraints on mantle potential temperature resolve the relationship between the MCR, the plume, Keweenaw LIP magmatism, and rapid plate motion, and indicate that an alternative mechanism, such as enhanced small-scale convection due to rapid plate motion and plume-lithosphere interaction, was required to generate the voluminous Main magmatic phase.

Investigating of the impact of biommetic pinna dynamics on sonar tasks in natural environments

Bats are known to perform incredible feats using their echolocation abilities, which include natural tasks, such as navigation through foliage and hunting prey, as well as tasks they have been trained to perform, such as classification of man-made objects. Much work has been done to engineer biomimetic systems that can perform these and similar tasks in a comparable way to bats. Biomimetic sonar devices have performed tasks such as identifying a geographic location, object classification, and foliage gap finding. Particular species of bats (notably those of the families Hipposideridae and Rhinolophidae) use rapid ear motion while making sonar calls, and the full effect and purpose of this motion is not fully understood. Our research goal is to perform sonar tasks with a biomimetic sonar head capable of both static and dynamic ear motion and investigate the effect of dynamic ear motion on captured echoes and performance on tasks. To this end, we have collected echo data in natural habitats with dense tropical vegetation in Brunei on the island of Borneo. Tasks currently under investigation include location identification and detection of man-made objects in foliage, and are performed by deep learning classifiers trained on echoes taken by the biomimetic sonar device.

Sub‐Lithospheric Small‐Scale Convection Tomographically Imaged Beneath the Pacific Plate

AbstractSmall‐scale convection beneath the oceanic plates has been invoked to explain off‐axis nonplume volcanism, departure from simple seafloor depth‐age relationships, and intraplate gravity lineations. We deployed 30 broadband ocean bottom seismometer stations on ∼40 Ma Pacific seafloor in a region notable for gravity anomalies, measured by satellite altimetry, elongated parallel to plate motion. P‐wave teleseismic tomography reveals alternating upper mantle velocity anomalies on the order of ±2%, aligned with the gravity lineations. These features, which correspond to ∼300°–500°K lateral temperature contrast, and possible hydrous or carbonatitic partial melt, are—surprisingly—strongest between 150 and 260 km depth, indicating rapid vertical motions through a low‐viscosity asthenospheric channel. Coherence and admittance analysis of gravity and topography using new multibeam bathymetry soundings substantiates the presence of mantle density variations, and forward modeling predicts gravity anomalies that qualitatively match observed lineations. This study provides observational support for small‐scale convective rolls beneath the oceanic plates.