Maximizing scanning speed in the ultrafast laser cutting of thin materials.

A mathematical model is derived to predict the maximum speed of a focused laser beam in the laser cutting of thin materials. This model contains only two material parameters and is used to obtain an explicit relationship between the cutting speed and laser parameters. The model shows that there exists an optimal focal spot radius with which cutting speed is maximized for a given laser power. We compare the modeling results with experiments and find a good agreement after correcting laser fluence. This work is useful for the practical application of lasers in processing thin materials such as sheets and panels.

Doubling the optical efficiency of VR systems with a directional backlight and a diffractive deflection film.

We demonstrate an approach to double the optical efficiency of virtual reality (VR) systems based on a directional backlight and a diffractive deflection film (DDF). The directional backlight consists of a commercial collimated light-emitting diode (LED) array and a two-layer privacy film, while the DDF is a three-domain Pancharatnam-Berry (PB) phase lens. Such a PB phase lens was fabricated by the zone exposure and spin-coating method. The focal length of each domain is designed according to the imaging optics of the VR system. Our approach works well in both Fresnel and "pancake" VR systems. We also build the corresponding models in LightTools, and the simulation results are in good agreement with experiment. In experiment, we achieved a 2.25x optical efficiency enhancement for both systems, which agrees with the simulation results (2.48x for Fresnel and 2.44x for "pancake" systems) well. Potential application for high efficiency VR displays is foreseeable.

Determining the influencing factors of preferential flow in ground fissures for coal mine dump eco-engineering.

Ground fissures (GF), appearing in front of dumps, are one of the most obvious and harmful geological hazards in coal mining areas. Studying preferential flow and its influencing factors in the ground fissures of dumps may provide basic scientific support for understanding the rapid movement of water and vegetation restoration and reconstruction in mining areas. Based on field surveys of ground fissures, three typical ground fissures were selected in the studied dump. The morphological characteristics of preferential flow for ground fissures were determined through field dye tracing, laboratory experiments, and image processing technology. The results indicated that the lengths of the three ground fissures ranged from 104.84 cm to 120.83 cm, and the widths ranged from 2.86 cm to 9.85 cm. All of the ground fissure area densities were less than 10%, and the proportion of ground fissure surface area was small in the dump. The maximum fissure depth was 47 cm, and the minimum was 16 cm. The ground fissure widths ranged from 0 cm to 14.98 cm, and the fissure width and fissure width-to-depth ratios decreased with increasing soil depth. The stained area was greater than 90% in the 0-5 cm soil layers of the three fissures, and water movement was dominated by matrix flow. The stained width decreased from 90 cm to 20 cm with increasing soil depth. The preferential flow was mainly concentrated on both sides of the fissure, which was distributed as a "T" shape. The preferential flow stained area ratios were 27.23%, 31.97%, and 30.73%, respectively, and these values decreased with increasing soil depth. The maximum stained depths of the preferential flow among the three fissures were different, and the maximum stained depth of GF II was significantly larger than that of GF I and GF III (P < 0.05). The stained path numbers of the three fissures ranged from 0 to 49. With increasing soil depth, the stained path number first increased and then decreased. The stained path widths of the three fissures ranged from 0 cm to 90 cm. With the increase in soil depth, the stained path width decreased. The stained area ratio was significantly positively correlated with ground fissure width, the ground fissure width-to-depth ratio, soil saturated hydraulic conductivity, soil organic matter, and sand content and was significantly negatively correlated with soil water content and clay content. The stained path number was significantly positively correlated with ground fissure width, the ground fissure width-to-depth ratio, soil saturated hydraulic conductivity and soil organic matter. The stained path width was significantly positively correlated with the ground fissure width-to-depth ratio, soil saturated hydraulic conductivity, soil organic matter and sand content and was significantly negatively correlated with clay content. Plant roots could significantly increase the stained area ratio, stained path number, and width and promote the formation and development of preferential flow.

Electrochemical Profile Recording for Pueraria Variety Identification.

The rapid identification of plant variety is valuable in both academic studies and crop production. However, rapid and accurate identification has been difficult because many varieties have very similar morphological characteristics and are susceptible to the effects of the growing environment. In this work, we established an electrochemical method for recording the electro-active profile of compounds in plant tissue. Because the chemical composition of different varieties is largely controlled by their genes, rather than a growing environment, this method has considerable potential for variety identification. Three varieties of Pueraria with sixteen locations were collected for confirming the feasibility of the proposed methodology. Principal component analysis and peak ratio analysis have been used for grouping the sample data. The results indicate the electrochemical profiles of three varieties can be distinguished using their voltammetric data.

A review of microplastics in the aquatic environmental: distribution, transport, ecotoxicology, and toxicological mechanisms.

The interactions between microplastics (MPs) and aquatic organisms are becoming increasingly frequent due to the extensive distribution of MPs in aquatic environments. MPs from the aquatic environment tend to accumulate and move through living organisms. Therefore, MPs can affect human health though the food chain and human consumption. In this brief review, the environmental distribution, sources, and transport of MPs are reviewed, and the potential consequences of the presence of MPs in the aquatic environment to human food are discussed. This review also summarized the toxicity effects and toxicity mechanisms of MPs based on various environmentally relevant test species and discussed the combined toxicity effects of MPs and various pollutants in aquatic ecosystems. The knowledge of the adverse effects on combined toxicity and the mechanism of MPs toxicity are very limited. Thus, a systematic assessment of the aquatic environmental risk in various species from MPs is challenging. In the end, we identify the knowledge gaps that need to be filled and provide suggestions for future research.

Temperature and pH effects on biophysical and morphological properties of self-assembling peptide RADA16-I.

It has been found that the self-assembling peptide RADA 16-I forms a beta-sheet structure and self-assembles into nanofibers and scaffolds in favor of cell growth, hemostasis and tissue-injury repair. But its biophysical and morphological properties, especially for its beta-sheet and self-assembling properties in heat- and pH-denatured conditions, remain largely unclear. In order to better understand and design nanobiomaterials, we studied the self-assembly behaviors of RADA16-I using CD and atomic force microscopy (AFM) measurements in various pH and heat-denatured conditions. Here, we report that the peptide, when exposed to pH 1.0 and 4.0, was still able to assume a typical beta-sheet structure and self-assemble into long nanofiber, although its beta-sheet content was dramatically decreased by 10% in a pH 1.0 solution. However, the peptide, when exposed to pH 13.0, drastically lost its beta-sheet structure and assembled into different small-sized globular aggregates. Similarly, the peptide, when heat-denatured from 25 to 70 degrees C, was still able to assume a typical beta-sheet structure with 46% content, but self-assembled into small-sized globular aggregates at much higher temperature. Titration experiments showed that the peptide RADA16-I exists in three types of ionic species: acidic (fully protonated peptide), zwitterionic (electrically neutral peptide carrying partial positive and negative charges) and basic (fully deprotonated peptide) species, called 'super ions'. The unordered structure and beta-turn of these 'super ions' via hydrogen or ionic bonds, and heat Brownian motion under the above denatured conditions would directly affect the stability of the beta-sheet and nanofibers. These results help us in the design of future nanobiomaterials, such as biosensors, based on beta-sheets and environmental changes. These results also help understand the pathogenesis of the beta-sheet-mediated neuronal diseases such as Alzheimer's disease and the mechanism of hemostasis.