Phenomenon In Natural World Research Articles

Research on the Sedimentation of Spherical-Particle Aggregations

The sedimentation of spherical-particle aggregations is the common phenomenon in natural world. However, the related research is quite limited. In this study, the spherical particles with four different densities and three diameters were first used for preparing aggregations with two, three and four particles, respectively. And then the final settling velocity of the aggregations was measured using a visual vertical pipe column. It was found that the final settling velocity would increase with the density and the diameter of the unit particle, which is well in agreement with the Stokes’ theory. Furthermore, the geometry arrangement of the particles can also affect the settling velocity significantly, but no model available to consider its influence. With the increase of particle number, the final velocity presents increase tendency.

An area and power efficient adder-based stepwise linear interpolation for digital signal processing

Linear interpolation is frequently used in digital signal processing applications to reconstruct signals, e.g., image, and audio processing, for which the multiplier and divider are two power- and area-hungry operators. Since most natural world phenomena are not exactly representable in linear forms, it is inefficient to use multiplier-based linear interpolation (MBLI) for accurate linear curve fitting. In this paper, area- and power-efficient adder-based stepwise linear interpolation (ABSI) is proposed to emulate the behavior of conventional linear interpolation. As a test vehicle for system demonstrations and performance evaluations, a general purpose display controller for applying an interpolationbased image/video scaling engine and overdrive for multimedia displays such as televisions, monitors, and projectors, was designed. Compared with a scaling engine using conventional MBLI, a scaling engine using the proposed ABSI has a similar scaling quality in terms of the peak signalto- noise ratio (PSNR), while reducing the area and power consumption by 45% and 44%, respectively. Furthermore, as compared with the compression/decompression of an overdrive using conventional MBLI, the data compression/decompression of the overdrive with the proposed ABSI shows a comparable compression/ decompression quality while reducing the area and power consumption by 46% and 45%, respectively.

Surface Engineering Method to Fabricate a Bendable Self-Cleaning Surface with High Robustness

Self-cleaning is a common phenomenon in natural world and has wide applications in people's real life. Here we report a general surface engineering method to fabricate micro/nano hybrid structure on polymer film, which can be applied to other substrates. The modified polymer surface is superhydrophobic with a water contact angle (CA) of 160 +/- 1 degrees and a water sliding angle (SA) of 3 degrees. When bent to two opposite directions, the convex surface and concave surface are still superhydrophobic and exhibit self-cleaning property. Dusts with different sizes can be cleared away from the modified surface by dipping water drops or spraying water mist. The surface engineering method modified surface has ultrahigh robustness. Its perfect multi-scale hierarchical structure and self-cleaning property barely change even after undergoing one hour ultrasonic oscillation. This method is applicable to modify the surfaces of various materials, architectures and devices into self-cleaning surfaces.

Self-Organized Criticality Underlies Arrhythmogenic Calcium Waves in Cardiac Myocytes

In cardiac myocytes, calcium (Ca)-induced Ca release can give rise to propagating Ca waves that promote cardiac arrhythmias. To understand the mechanism underlying the transition from localized Ca sparks to global Ca waves, we developed a mathematical model of a spatially-distributed network of diffusively coupled Ca release units (CRUs) comprised of junctional/longitudinal sarcoplasmic reticulum and dyadic/cytoplasmic spaces with physiologically realistic dimensions. As total Ca was increased in the model, Ca spark cluster sizes initially exhibited an exponential distribution, which transitioned to a scale-free power-law (f-β) distribution near the threshold at which random Ca sparks transitioned to Ca waves. The power-law relationship indicates that Ca release patterns in the CRU network are governed by a dynamical mechanism called self-organized criticality, the same process underlying many natural world phenomena such as avalanches and earthquakes. We tested this prediction experimentally in saponin-permeabilized cardiac myocytes. As free Ca, buffered with 0.5 mM EGTA, was increased, Ca spark cluster size transitioned from an exponential distribution to a power-law distribution at a free Ca concentration of 400 nM. Consistent with self-organized criticality, this Ca concentration was near the threshold for spark-to-wave transition since fully propagating waves were observed above 400 nM Ca. Below this concentration, Ca was released mostly as individual sparks, and spark cluster sizes followed an exponential rather than power-law distribution. In conclusion, our findings provide both theoretical and experimental evidence that the transition from Ca sparks to arrhythmogenic Ca waves in cardiac myocytes is mediated by the dynamical process of self-organized criticality, common to many natural phenomena. This provides a theoretical framework for developing interventions which modulate the Ca spark-to-wave transition threshold as a potential therapeutic strategy for preventing arrhythmias.