Appearance Of Ripples Research Articles

Periodic ripple of coda envelope observed in northeastern Japan

We have investigated the SH envelopes (bandpass filtered and mean squared seismograms) in the early coda of local and regional earthquakes observed at five stations in northeastern Japan. The most remarkable feature we have found is a periodic increase in coda amplitude with nearly a constant time interval of several seconds. We call this phenomena ‘ripple’ of coda envelope. We examined four possible origins of periodic ripple: an artifact due to inadequate data handling, repeated source radiation, site effect, and path-originated phase. The possibility of artifact due to inadequate filtering or smoothing is low because the ripple is visible in both unfiltered seismograms and filtered traces with various filtering parameters. Repeated source radiation is not responsible for the ripple, because the ripple has longer time duration than that of source time function of the investigated events, and because the appearance of ripple at five stations is not synchronous. Local site amplification factors determined by the spectral ratio of horizontal to vertical motions suggest the contribution of surficial low velocity layers (LVL) to the periodic ripple. The events with prominent ripple are predominantly distributed in shallow range off the Pacific coast and intermediate-depth range along the volcanic front of the Japanese Islands. This trend is commonly observed for all the investigated stations having different site amplification factors. This observation is suggestive of a path-dependent origin such as trapped waves in the LVL in the upper part of the subducting slab. Thus the guided waves trapped in the LVL are the probable origin of the periodic ripple. The LVL is either the surficial sedimentary layers under the recording site or the subducting oceanic crust.

Beta 2 microglobulin haemodialysis related amyloidosis: distinctive gross features of gastrointestinal involvement.

Two cases of beta 2 microglobulin amyloidosis following long term haemodialysis found during necropsy are reported. The patients were 59 and 65 year old Japanese men, respectively. In both cases,...

The effect of various base/core materials on the setting of a polyvinyl siloxane impression material

Five resin-modified glass ionomers and amalgam, used as a base or core buildup material, were clinically evaluated for whether they effected polymerization of a low viscosity (light body) regular set polyvinyl siloxane impression material. A total of 20 samples per group was prepared according to the manufacturer's recommendations. Ten samples from each group were handled with latex gloves during mixing and the other 10 were handled with vinyl gloves. Five of the 10 samples had the outer surface prepared with a round diamond wheel. Impressions were made of all the samples. The impression materials were visually scored inhibited or noninhibited. Inhibited impression materials met at least one following criterion: (1) an oily substance on the surface of the impression readily collected on a sterile explorer tine as it was moved across the impression surface; (2) a rippled appearance on the surface of the impression material; or (3) unpolymerized impression material adherent to the prepared sample surface. If none of the criteria were observed, the impression was scored noninhibited. The data were analyzed with the chi square analysis (level of significance p = 0.05). Total chi square analysis revealed a significant difference between brands ( p = 0.0001) and between prepared and non-prepared samples ( p = 0.001). Interrater reliability data were analyzed with the kappa correlation analysis. Raters were in complete agreement (kappa = +1). The prepared samples of Vitrebond material had an inhibitory effect on the polymerization of Express impression material.

Sea ripple formation: the heterogeneous sediment case

Ripple formation beneath sea waves is analyzed both by experimental and analytical means when the bottom is made up of a mixture of sands. An oscillatory flow is obtained in a closed duct by the oscillations of two rigidly connected pistons located at the ends of the duct. The amplitude and period of the oscillations can be continuously varied. A fixed tray, located at the bottom of the duct and filled with different types of sediments, allows ripple formation to be observed. The presence of graded sediments is found to have a stabilizing effect and causes longer ripples to appear. Moreover a selective sediment transport is observed and quantified which tends to pile up the coarse grains at ripple crests leaving the fine ones in the troughs. As in the companion paper, the theory is based on a linear stability analysis of a flat sandy bottom subject to an oscillatory flow. Because of the presence of a mixture, a modified version of Exner equation is used and an “hiding” factor should be inserted in the sediment transport rate formula. The flow regime in the bottom boundary layer is assumed to be turbulent. The conditions for ripple appearance are determined along with their wavelengths as they form. Good agreement is found between experimental data and theoretical findings.

Sea ripple formation: the turbulent boundary layer case

This study presents a predictive theory of ripple formation beneath sea waves. The theory is based on a linear stability analysis of a flat sandy bottom subject to an oscillatory flow. The flow regime in the bottom boundary layer is assumed to be turbulent; hence previous works on the subject, which considered a laminar flow, are extended in a more relevant range of the Reynolds number. The turbulent stresses are described by means of the constant eddy viscosity model proposed by Sleath in 1991 and a two time-scale approach is used to decouple fluid motion from bottom time development. A closed form solution is found for the turbulent oscillatory flow over a fixed wavy wall and the time development of the bottom perturbation is determined by means of sediment continuity equation. The conditions for ripple appearance are determined along with their wavelength as they form. A comparison between theoretical findings and experimental data supports the validity of the present approach.

Organization and disorganization of actin filaments in human epidermal keratinocytes: Heat-shock treatment and recovery process

We investigated alterations of actin organization due to heat shock and recovery from the collapse in human epidermal keratinocytes. Exposure of keratinocytes to elevated temperature caused the rapid disintegration of actin filaments. With a heat-shock treatment at 45 degrees C for 10 min, actin filaments disappeared and granular actin was distributed diffusely in the cytoplasm. After return to 37 degrees C, recovery of actin organization was observed. Completely disintegrated granular actin assembled to form actin dots, which tended to group. The grouping actin dots often took a circular, semicircular or arched form. Filamentous actin then extended out from the actin dots. Fine short bundles of actin filaments had a rippled appearance or were polygonal in structure, with actin filaments converged at many points. On the seventh day after heat-shock treatment, actin organization had almost returned to the pre-heat-shock condition, with diffusely distributed actin filaments. In previous studies, we observed such aberrant structures in human malignant keratinocytes and human epidermal keratinocytes treated with 12-O-tetradecanoylphorbol-13-acetate. The observations presented here indicate that those structures are not specific to malignancy or to the process of malignant transformation, but represent less mature and aberrant organizations of actin.

Distribution of actin filaments in human malignant keratinocytes

Distribution of actin filaments in human malignant keratinocytes was examined by immunofluorescence staining. The primary cultures were obtained from a squamous cell carcinoma, a basal cell carcinoma, and Bowen's disease. Rhodamine-phalloidln staining revealed that actin filaments were occasionally organized to form stress fibers, many short bundles with a ripple appearance, and regular arrays of actin patches. Some of these structures appeared in untransformed keratinocytes as a result of a brief exposure to a tumor promotor, TPA. These findings suggest that regulation of actin functions is involved in neoplastic processes from the very early stages and that alteration is persistent in neoplastic cells.

Modal properties of unstable resonator semiconductor lasers with a lateral waveguide

The modal properties of unstable resonator lasers with a lateral waveguide have been analyzed, and an unstable resonator semiconductor laser with a real index lateral waveguide has been demonstrated. Output powers in excess of 400 mW were observed with a stable, highly coherent lateral field distribution. The incorporation of a lateral real index waveguide with the unstable resonator configuration results in an increase in the external quantum efficiency and the appearance of ripples in the lateral field distribution.

A continuum model for a red blood cell transformation: Sphere to crenated sphere

The evolution of crenations on the spherical red blood cell, which is part of the reversible disc-sphere transformation of these cells, is considered here. A continuum model is developed where the cell is treated as a small viscous droplet encapsulated by a viscoelastic solid membrane. When a small amount of material is deposited into the membrane, the drop responds by increasing its surface area as manifested by the appearance of ripples. A preferred number of crenations form and they are sustained for long time periods. The inception of crenations is due to a dynamic instability in the governing set of nonlinear equations, and depends on the rheological properties of the droplets' interior and membrane.

Patterns of filipin-sterol complex distribution in intact erythrocytes and intramembrane particle-aggregated ghost membranes.

When fixed erythrocytes are exposed to the cholesterol probe, filipin, and freeze-fractured, their membrane is labeled with only a limited number of typical, 25 nm diameter filipin-sterol complexes. In addition, the membrane contains many less distinct filipin-induced perturbations that give it an overall rippled appearance. In contrast, red cell ghosts subjected to conditions that result in an aggregation of their intramembrane particles have large particle-free membrane domains which are completely filled with 25 nm filipin-sterol complexes. These results suggest that some constraint exists in the intact erythrocyte membrane which restricts the formation of typical filipin-sterol complexes.