A Fiber Sliding-Orientation Based Micromechanics Failure Model for Melt-Blown Nonwovens.

The mechanical model of melt-blown nonwovens (MNs) serves as the foundation for performance optimization, which can offer helpful guidance for product material selection, structural design, and cost control. However, it is challenging to describe the micromechanics failure mechanism of MNs using the traditional mechanical model, which aims to match the model curve with the experimental result at the macrolevel. Herein, a micromechanics failure model for MNs based on sliding-orientation competition is developed. Through in situ observations of fiber position changes and the fluctuation of stress-strain curves, fiber sliding and orientation are introduced into the failure process of MNs. Due to fiber bonding and static friction, only orientation happens during the first stage of stretching. In dramatic contrast, the fibers will slide and orient in the second stage of stretching to change their positions in response to the external force. Sliding friction, fiber bonding, and static friction make up the stress of MNs, and the conflict of fiber sliding and orientation causes variations in the stress. The model has been successfully applied to polylactic acid (PLA) MNs, which proves the effectiveness of the model in MNs.

[Strenthening entry-exit supervision for protecting natural resources of traditional Chinese medicine].

China is highly rich of medicinal plants. Traditional Chinese medicine(TCM) has a long history and is important traditional resources in China. As one of the important strategic resources and the link among all the countries along the ancient "Silk Road", TCM has played important role in economy, politics, society and ecology. With the initiative of the "Belt and Road" in recent years, many natural resources of TCM now are facing the risk of extinction due to more and more frequent trade between China and other countries, also the increase of export has influenced to the stock of TCM. In order to prevent the loss of the resources, strengthen the protection and sustainable use of TCM, our study provided the strategies to the natural resources of TCM's entry-exit supervision from nine aspects, like law and regulation system, based on the analysis of current supervision status quo.

Diphylleia Grayi-Inspired Intelligent Temperature-Responsive Transparent Nanofiber Membranes.

Nanofiber membranes (NFMs) have become attractive candidates for next-generation flexible transparent materials due to their exceptional flexibility and breathability. However, improving the transmittance of NFMs is a great challenge due to the enormous reflection and incredibly poor transmission generated by the nanofiber-air interface. In this research, we report a general strategy for the preparation of flexible temperature-responsive transparent (TRT) membranes, which achieves a rapid transformation of NFMs from opaque to highly transparent under a narrow temperature window. In this process, the phase change material eicosane is coated on the surface of the polyurethane nanofibers by electrospray technology. When the temperature rises to 37 °C, eicosane rapidly completes the phase transition and establishes the light transmission path between the nanofibers, preventing light loss from reflection at the nanofiber-air interface. The resulting TRT membrane exhibits high transmittance (> 90%), and fast response (5 s). This study achieves the first TRT transition of NFMs, offering a general strategy for building highly transparent nanofiber materials, shaping the future of next-generation intelligent temperature monitoring, anti-counterfeiting measures, and other high-performance devices.

Polylactic Acid/Calcium Stearate Hydrocharging Melt-Blown Nonwoven Fabrics for Respirator Applications.

Non-biodegradable polypropylene, which poses a serious threat to the environment, is the most utilized material in air filtration systems. Moreover, under conditions of high temperature and high humidity, the electrostatic charge in melt-blown nonwoven fabrics treated with traditional corona electrets will quickly dissipate. Here, biodegradable polylactic acid, calcium stearate, and an innovative hydrocharging technique are reported to develop environmentally friendly polylactic acid/calcium stearate hydrocharging melt-blown nonwoven fabrics with high charge stability. Compared with polylactic acid melt-blown nonwoven fabrics, the crystallization structure and charge storage of polylactic acid/calcium stearate melt-blown nonwoven fabrics have been greatly improved due to the presence of calcium stearate. In PM0.3, it exhibited a high filtration efficiency (96.78%), a low pressure drop (65.20 Pa), and a good quality factor (0.053 Pa-1), which can meet the N95 respirator standard. Furthermore, it is worth mentioning that the filtration performance remained at a high level (>95.00%) after 2 months. Importantly, based on the test and analysis of surface electrostatic potential, crystallization, and charge storage and distribution, we proposed plausible charge generation and stable storage mechanisms. It demonstrated more potential for electret air filtration and smart respirators as the further possible step of research in the field.

Highly Transparent Nanofibrous Membranes Used as Transparent Masks for Efficient PM0.3 Removal.

Currently, the quest for highly transparent and flexible fibrous membranes with robust mechanical characteristics, high breathability, and good filtration performance is rapidly rising because of their potential use in the fields of electronics, energy, environment, medical, and health. However, it is still an extremely challenging task to realize transparent fibrous membranes due to serious surface light reflection and internal light scattering. Here, we report the design and development of a simple and effective topological structure to create porous, breathable, and high visible light transmitting fibrous membranes (HLTFMs). The resultant HLTFMs exhibit good optical performance (up to 90% transmittance) and high porosities (>80%). The formation of such useful structure with high light transmittance has been revealed by electric field simulation, and the mechanism of fibrous membrane structure to achieve high light transmittance has been proposed. Moreover, transparent masks have been prepared to evaluate the filtration performance and analyze their feasibility to meet requirement of facial recognition systems. The prepared masks display high transparency (>80%), low pressure drop (<100 Pa) and high filtration efficiency (>90%). Furthermore, the person wearing this mask can be successfully identified by facial recognition systems. Therefore, this work provides an idea for the development of transparent, breathable, and high-performance fibrous membranes.

Metabolic cold adaptation in the Asiatic toad: intraspecific comparison along an altitudinal gradient.

The metabolic cold adaptation (MCA) hypothesis predicts an increase in metabolic rate and thermal sensitivity of poikilotherms from cold environments as compared to those from warm environments, when measured under standardized conditions. This compensatory response is also expected to evolve in life history and behavioral traits if the reductions in these phenotypic traits at low temperature involves in a reduction in fitness. We investigated the extent to which the level of energy intake (measured as feeding rate), energy turnover (measured as standard metabolic rate, SMR) and the energy budget (energy allocation to growth and physical activity) are influenced by climatic conditions in three populations of the Asiatic toad (Bufo gargarizans) distributed across an altitudinal gradient of 1350 m in the Qionglai Mountains of Western China. We found a similar thermal reaction norm of SMR at both population and individual levels; therefore, the data did not support the MCA hypothesis. However, there was a co-gradient variation (CoGV) for mass change rate in which the high and medium altitudinal populations displayed slower mass change rates than their counterparts from low altitudes. Moreover, this CoGV pattern was accompanied by a low feeding rate and high physical activity for the high- and medium-altitude populations. Our results highlight that adjustments in energy intake and energy allocation to behaviors, but not energy allocation to metabolism of maintenance, could act as an energetic strategy to accommodate the varied growth efficiency in Asiatic toads along an altitudinal gradient.

Molecular phylogeny and morphological comparisons of the genus Hebius Thompson, 1913 (Reptilia: Squamata: Colubridae) uncover a new taxon from Yunnan Province, China, and support revalidation of Hebius septemlineatus (Schmidt, 1925).

We describe a new species of the genus Hebius and provide evidence for the validity of H. septemlineatuscomb. nov. Morphological and molecular analyses of Hebius specimens collected in Yunnan Province, China, revealed three distinct lineages, namely the newly described Hebius weixiensissp. nov., as well as H. octolineatus (Boulenger, 1904), and H. septemlineatuscomb. nov. (Schmidt 1925), which is removed from synonymy with H. octolineatus. Based on mitochondrial genealogy, Hebius weixiensissp. nov. is sister to H. septemlineatuscomb. nov., while H. octolineatus is sister to H. bitaeniatus. The new species and H. septemlineatuscomb. nov. showed considerable genetic divergence from their recognized congeners (uncorrected P-distance ≥3.9%). Furthermore, the new species and H. septemlineatuscomb. nov. can be diagnosed from closely related congeners by a combination of pholidosis characters.

Urban-development-induced Changes in the Diversity and Composition of the Soil Bacterial Community in Beijing.

Numerous studies have implicated urbanization as a major cause of loss of biodiversity. Most of them have focused on plants and animals, even though soil microorganisms make up a large proportion of that biodiversity. However, it is unclear how the soil bacterial community is affected by urban development. Here, paired-end Illumina sequencing of the 16 S rRNA gene at V4 region was performed to study the soil microbial community across Beijing's built-up area. Proteobacteria, Acidobacteria, Bacteroidetes, Actinobacteria, Gemmatimonadetes, Verrucomicrobia, Planctomycetes, and Chloroflexi were the dominant phyla in all samples, but the relative abundance of these phyla differed significantly across these concentric zones. The diversity and composition of the soil bacterial community were found to be closely correlated with soil pH. Variance partitioning analysis suggested that urban ring roads contributed 5.95% of the bacterial community variation, and soil environmental factors explained 17.65% of the variation. The results of the current work indicate that urban development can alter the composition and diversity of the soil microbial community, and showed pH to be a key factor in the shaping of the composition of the soil bacterial community. Urban development did have a strong impact on the bacterial community of urban soil in Beijing.