Inertial Events Research Articles

DyNeuMo Mk-1: Design and pilot validation of an investigational motion-adaptive neurostimulator with integrated chronotherapy

There is growing interest in using adaptive neuromodulation to provide a more personalized therapy experience that might improve patient outcomes. Current implant technology, however, can be limited in its adaptive algorithm capability. To enable exploration of adaptive algorithms with chronic implants, we designed and validated the ‘Picostim DyNeuMo Mk-1’ (DyNeuMo Mk-1 for short), a fully-implantable, adaptive research stimulator that titrates stimulation based on circadian rhythms (e.g. sleep, wake) and the patient's movement state (e.g. posture, activity, shock, free-fall). The design leverages off-the-shelf consumer technology that provides inertial sensing with low-power, high reliability, and relatively modest cost. The DyNeuMo Mk-1 system was designed, manufactured and verified using ISO 13485 design controls, including ISO 14971 risk management techniques to ensure patient safety, while enabling novel algorithms. The system was validated for an intended use case in movement disorders under an emergency-device authorization from the Medicines and Healthcare Products Regulatory Agency (MHRA). The algorithm configurability and expanded stimulation parameter space allows for a number of applications to be explored in both central and peripheral applications. Intended applications include adaptive stimulation for movement disorders, synchronizing stimulation with circadian patterns, and reacting to transient inertial events such as posture changes, general activity, and walking. With appropriate design controls in place, first-in-human research trials are now being prepared to explore the utility of automated motion-adaptive algorithms.

Mesoscale inertial transition in granular materials

Granular assemblies can experience complex failure patterns along a given loading path, with a distribution of ephemeral inertial events marked by local outbursts in kinetic energy. However, investigating such mechanisms appears to be necessary to understand how a certain failure mode develops in a granular material. Using a discrete element method, this study highlights several microstructure reorganizations before the specimen reaches a proper failure state. Meso structures have proven to be efficient to understand the elementary mechanisms responsible for these outbursts in kinetic energy. Strain–like and stress-like quantities are thus defined at a mesoscale and they are used to characterize the nucleation and propagation of these local microstructural events.

Effect of conservation of spatial volume on momentum, time, and speed of light

This essay considers that free-space appears to be composed of an energy field with characteristics of an elastic medium evenly dispersed across the Cosmos in an optimal high state of entropy. This spatial energy field or SEF has properties that may explain inertia and gravity. Linear and angular momentum appear to emerge from these properties. SEF is stretched and compressed in the presence of mass. In addition, compression of space by high inertial events slows the flow of time, similar to gravitational time dilation. This is presented as a new concept and called inertial time dilation. Also, it is proposed that the speed of light c is an intrinsic self-imposed limit due to characteristics of space (SEF) as exemplified by the physical constants ε o and μ o representing electric permittivity and magnetic permeability.

Rate-state friction in microelectromechanical systems interfaces: Experiment and theory

A microscale, multi-asperity frictional test platform has been designed that allows for wide variation of normal load, spring constant, and puller step frequency. Two different monolayer coatings have been applied to the surfaces—tridecafluorotris(dimethylamino)silane (FOTAS, CF3(CF2)5(CH2)2 Si(N(CH3)2)3) and octadecyltrichlorosilane (OTS, CH3(CH2)17SiCl3). Static friction aging was observed for both coatings. Simulating the platform using a modified rate-state model with discrete actuator steps results in good agreement with experiments over a wide control parameter subspace using system parameters extracted from experiments. Experimental and modeling results indicate that (1) contacts strengthen with rest time, exponentially approaching a maximum value and rejuvenating after inertial events, and (2) velocity strengthening is needed to explain the shorter than expected length of slips after the friction block transitions from a stick state. We suggest that aging occurs because tail groups in the monolayer coatings reconfigure readily upon initial contact with an opposing countersurface. The reconfiguration is limited by the constraint that head groups are covalently bound to the substrate.

Characteristics and Mechanisms of Low-Level Jets in the Yangtze River Delta of China

A dataset obtained using a wind-profile radar located at the Yangtze River Delta in China (\(31.14^{\circ }\)N, \(121.81^{\circ }\)E) in 2009 was used to investigate the characteristics and evolution of low-level jets (LLJs) along the east China coast. The study investigated the daily and seasonal structures of LLJs as well as several possible causes. A total of 1,407 1-h LLJ periods were detected based on an adaptive definition that enabled determination of four LLJ categories. The majority (77 %) of LLJs were found to have speeds \(<\)14.0 m s\(^{-1}\) (maximum of 34.6 m s\(^{-1})\) and occur at an average altitude below 600 m (76 % of the observed LLJs). The dominant direction of the LLJs was from the south-south-west, which accounted for nearly 32 %, with the second most common wind direction ranging from \(040^{\circ }\) to \(100^{\circ }\), albeit with a number of stronger LLJs from the west-south-west. A comparison of LLJs and South-west Jets revealed that the frequencies of occurrence in summer are totally different. Results also revealed that in spring and summer, most LLJs originate from the south-south-west, whereas in autumn and winter, north-east is the dominant direction of origin. The peak heights of LLJs tended to be higher in winter than in other seasons. The horizontal wind speed and peak height of the LLJs displayed pronounced diurnal cycles. The Hilbert–Huang transform technique was applied to demonstrate that the intrinsic mode functions with a cycle of nearly 23 h at levels below 800 m, and the instantaneous amplitudes of inertial events (0.0417–0.0476 h\(^{-1}\) frequencies) have large values at 300–600 m. The variations in the occurrences of LLJs suggested connections between the formation mechanisms of LLJs and the South-west Jet stream, steady occupation of synoptic-scale pressure system, and land–sea temperature contrasts.

Diurnal–inertial motions and diapycnal mixing on the Portuguese shelf

This work presents observations of diurnal–inertial motions forced by a sea–land breeze regime near critical latitudes ( 30 ∘ ± 10 ∘ N / S ) for resonance on the Portuguese shelf. Wind conditions were determined with an Aanderaa meteorological buoy placed in the Bay of Setúbal during the Maritime Rapid Environmental Assessment 2004 (MREA04) sea trial. Currents data for this period were recorded from two Barny ADCP (acoustic Doppler current profiler) deployments located on the north and south sides of the bay, respectively. Both ADCPs covered almost the full depth of water ( ∼ 112 m ) with 24 bins of 4 m size at both sites. Dominant motions exhibited a two-layer configuration in response to energetic out-of-phase oscillations driven by diurnal–inertial currents. Hence, simultaneous CTD (conductivity, temperature, depth) data were considered to assess the strength of observed motions in promoting diapycnal mixing. With this aim, ADCP and CTD data were used to analyse the vertical shear ( S 2), squared buoyancy frequency ( N 2) and gradient Richardson number ( Ri) of the water column in terms of two main layers with highly stratified and vertically sheared flows during diurnal–inertial events. Observations show a strong variation in the vertical density field near both ADCP deployments that involved high vertical shears distributed into two layers associated with diurnal–inertial currents. The results of our analysis highlight the role of wind-forced diurnal–inertial motions in shelf areas near the critical latitudes, where they can greatly contribute to triggering diapycnal mixing at the scale of a few days, owing to sea–land breeze forcing.

The characteristics of near-surface velocity during the upwelling season on the northern Portugal shelf

Observations made on the northern Portugal mid-shelf between May 13 and June 15, 2002 were used to characterise the near-surface velocity during one upwelling season. It was found that in the surface mixed layer, the ‘tidal current’ was diurnal, but the tidal elevation was semi-diurnal. Both the residual current and the major axes of all tidal constituents were nearly perpendicular to the isobaths and the tidal current ellipses rotated clockwise; the major axis of the major tidal ellipse was about 3 cm s−1. The extremely strong diurnal current in the surface layer was probably due to diurnal heating, cooling, and wind mixing that induced diurnal oscillations, including the diurnal oscillation of wind stress. The near-inertial spectral peaks occurred with periods ranging from 1047 min to 1170 min, the longest periods being observed in deeper layers, and the shortest in the surface layer. Weak inertial events appeared during strong upwelling events, while strong inertial events appeared during downwelling or weak subinertial events. The near-inertial currents were out of phase between 5 m and 35 m layers for almost the entire measurement period, but such relationship was very weak during periods of irregular weak wind. Strong persistent southerly wind blew from May 12 to 17 and forced a significant water transport onshore and established a strong barotropic poleward jet with a surface speed exceeding 20 cm s−1. The subinertial current was related to wind variation, especially in the middle layers of 15 m and 35 m, the maximum correlation between alongshore current and alongshore wind was about 0.5 at the 5 m layer and 0.8 at the 35 m layer. The strongest correlation was found at a time lag of 20h in the upper layer and of 30h in the deeper layer. The wind-driven surface velocity obtained from the PWP model had maximum amplitude of about 7 cm s−1, corresponding to a wind stress at 0.1 Pa, and the horizontal velocity shear due to thermal wind balance had the order of 3 cm s−1. So the local wind and thermal wind would only explain a part of the strong surface velocity variations.

Effect of ultrasound on nucleated erythrocytes

In this experimental study, carp erythrocytes were used as nucleated cell models to test the hypothesis that ultrasound (US) exposure can cause the change in plasma membranes and hemoglobin. To identify target cell damage, we studied hemolysis, osmotic fragility, lipid peroxidation of red blood cells and oxidation of hemoglobin in the erythrocytes. The erythrocytes were exposed to 1 MHz continuous-wave US at the intensities of 0.61 to 2.44 W/cm 2 for 5 min. These results showed that US sonication at the intensities of 1.90 and 2.44 W/cm 2 led to an increase in the degree of hemolysis and, at the highest used intensity (2.44 W/cm 2), an increase in osmotic fragility. Ultrasound in all the used intensities induced an increase in lipid peroxidation. The results obtained showed that the level of methemoglobin has a tendency to increase after US exposure. Our results suggest that the changes in biomembranes can be due to inertial cavitation induced by US, but we cannot say which stage of the inertial event causes the damage. (E-mail: tgabryl@biol.uni.lodz.pl)

Inertial currents in the Indian Ocean derived from satellite tracked surface drifters

Satellite-tracked surface drifters were used to analyze the characteristics of inertial currents in the tropical Indian Ocean. The drifters were drogued at 15 m depth and had wind-produced slips less than 0.1 % of the wind speed. The rotary spectra of surface velocity components indicated the significance of inertial currents. They are circular (rotary coefficient >0.5), highly intermittent and contribute up to 46 % to the total kinetic energy of the surface flow field. Events of inertial activity, either triggered by the passage of atmospheric disturbances or by the local fluctuations in the atmospheric pressure (winds), did not last for more than 4 to 5 inertial cycles. The observed inertial frequency exhibited a shift towards the red end of the spectrum by 12 %. Cyclonic storm induced inertial events even at a location 300 km away from it.

Acoustic deinking of paper: Pulse effectiveness in particle detachment

Deinking remains an important step in environmentally conscious manufacturing of paper. Removing xerographic ink from a print sample using acoustic microcavitation provides an easy method to observe context for studying cavitation-induced erosion at surfaces. Experiments indicate that microcavitation evolves microimplosions which are effective in causing deinking preferentially at ink sites. Acoustic microcavitation is brought about by low megahertz acoustic fields giving rise to micron-size bubbles that live a few microseconds. In exposing a surface to continuous waves for a defined duration, one could obtain cavitation effects in an average, overall sense; the details of nucleation, evolution of inertial events, and the precise interplay of field parameters in effecting cavitation, however, get glossed over. Studying pulsed cavitation using tone bursts at low duty cycles, instead of CW insonification, reveals interesting details of the initiation and evolution of acoustic microcavitation. Specifically, it is found that short-pulse deinking is more effective than long-pulse deinking. This fact seems to raise an anomalous question of how the sample knows it is being visited by a short pulse or a long pulse. Recent experiments operationally demonstrate why short-pulse deinking is more effective. [Work supported by NSF.]

Susceptibility of silicon wafers to acoustic microcavitation damage

Acoustic methods are being increasingly used in semiconductor processing. Given the increase in circuit densities being implemented on semiconductor chips the requirements for particulate contamination tolerance are becoming more stringent. The semiconductor industries road-mapped specifications for 1998, 0.25 μm feature size require control of all particulate contaminants larger than 0.08 μm. Fine cleaning of post CMP wafers is currently being done by using the megasonics process. The cleaning effectiveness depends on the strength of the acoustic fields used. In using high-intensity, high-frequency acoustic fields it is crucial to ensure that the surface of the silicon wafer does not suffer any damage due to cavitation. This paper assesses the damage potential of semiconductor wafers to acoustic microcavitation. Acoustic microcavitation is brought about by low megahertz acoustic fields giving rise to micron size bubbles that live a few microseconds. In exposing a surface to continuous waves one could obtain cavitation effects in an average, overall sense; the details of nucleation, evolution of inertial events, however, get glossed over. Both, pulsed and cw insonification were studied. Experimental measurements of the thresholds for cavitation damage of semiconductor wafers will be presented.

Acoustic microcavitation at surfaces: New results in deinking of paper

Deinking remains an important step in environmentally conscious manufacturing of paper. A novel method based on acoustic microcavitation is used for deinking xerographic ink from paper. Microcavitation evolves microimplosions, which are effective in causing deinking preferentially at ink sites. Acoustic microcavitation is brought about by low megahertz acoustic fields giving rise to micron-sized bubbles that live a few microseconds. In exposing a surface to continuous waves for a defined duration one could obtain cavitation effects in an average, overall sense; the details of nucleation, evolution of inertial events, and the precise interplay of field parameters in effecting cavitation, however, get glossed over. Studying pulsed cavitation using tone bursts at low duty cycles, instead of CW insonification, reveals interesting details of the initiation and evolution of acoustic microcavitation. Experiments indicate that the 2-D context of how a xerographic print is deinked might be useful in inferring some attributes of 3-D pulp deinking. Assuringly, the results indicate that paper fibers are entirely undamaged, and the ink separation leaves them immaculately white, and that acoustic methods for deinking are a viable, chemical free, environmentally responsible means of recycling paper.

Evidence of inertial oscillations of the surface wind at Marcus Island

Near‐inertial oscillations of the surface wind were observed at Marcus Island (24°N, 154°E) in the subtropical Pacific area. Kinetic energy spectra of the surface wind show a peak at a period of 1.1 days in the clockwise component spectrum. This period is slightly (6%) shorter than the local inertial period (1.2 days). The peak period varies slightly during the record analyzed, but tends to remain below the local inertial period. Complex demodulation with a filter shows that the large inertial amplitudes occur intermittently and decay rapidly. Most of the occurrences of large inertial events seem to be related to passing cold frontal systems or migrating low‐pressure systems.

Inertial oscillations in the Irish Sea

An inertial current with a maximum speed of about 0.20 m s 1 was observed in June 1981, by a current meter 17 m below the surface of the thermally stratified waters of the western Irish Sea. The dynamics of the surface waters have been modelled using contemporary wind data recorded at the site to drive a horizontally unbounded surface slab 20 m deep with a velocity decay time of about three inertial periods (1.86 days). From thermistor chain data, inertial frequency potential energy was observed to radiate beneath the thermocline, descending at a rate of about 0.06 cm s 1. The energy available for internal mixing from the observed oscillation may have been as much as 80 J m 2, compared with 150 J m 2 from wind-induced surface mixing. The mean surface mixing power in summer is about7.1 × 10 4W m 2, while the mean shear-induced mixing power could be as much as2.0 × 10 4W m 2. The likely occurrence of strong inertial events has been estimated using the wind record fcr 10 successive summers at Dublin airport. Large oscillations with speeds 0.20m s 1, or mixed layer kinetic energy(MLKE) > 400 J m 2, have an average duration of about 28 h. They occur about once every 2 months between mid-May and mid-August but seem to be more frequent from then until mid-September. Moderate oscillations (MLKE > 200 J m 2) are more evenly distributed, occurring about once every 2 weeks. Small oscillations (MLKE > 40 J m 2) occur nearly 50% of the time.

Inertial Current in Lake Ontario, Winter 1972–73 (IFYGL)

Abstract Nearly four months of continuous current and temperature data, taking during the 1972–73 winter depths of about 15 and 75 m in Lake Ontario, have been analyzed for evidence of inertial oscillations. The data, collected as part of the International Field Year for the Great Lakes (IFYGL), were obtained at nine stations: one near midlake, about 40 km from shore, and in about 140 m of water; the other eight spaced around the lake, about 50 km apart, 12 km from shore and in 100 m of water. Inertial currents occurred in episodes lasting less than 5 days and had speeds less than 15 cm s−1. At the midlake and easternmost stations, the inertial currents accounted for as much as 10% (on average) of the total current variance. Some inertial events in midlake had no counterpart nearer shore. In contrast, a lakewide episode of inertial currents was induced by a storm during a two to three week period of vertical stratification. The average hodographs during the stratified period, calculated from bandpassed sh...