Search

Aerogel fibers with ultrahigh porosity, large specific surface area, and ultralow density have shown increasing interest due to being considered as the next generation thermal insulation fibers. However, it is still a great challenge to fabricate arbitrary aerogel fibers via the traditional wet-spinning approach due to the obvious conflict between the static sol-gel transition of the aerogel bulks and the dynamic wet-spinning process of aerogel fibers. Herein, a sol-gel confined transition (SGCT) strategy was developed for fabricating various mesoporous aerogel fibers, in which the aerogel precursor solution was first driven by the surface tension into the capillary tubes, then the gel fibers were easily formed in the confined space after static sol-gel process, and finally the mesoporous aerogel fibers were obtained via the supercritical CO2 drying process. As a typical case, the polyimide (PI) aerogel fiber prepared via the SGCT approach has exhibited a large specific surface area (up to 364 m2/g), outstanding mechanical property (with elastic modulus of 123 MPa), superior hydrophobicity (with contact angle of 153°), and excellent flexibility (with curvature radius of 200 μm). Therefore, the aerogel woven fabric made from PI aerogel fibers has possessed an excellent thermal insulation performance in a wide temperature window, even under the harsh environment. Besides, arbitrary kinds of aerogel fibers, including organic aerogel fibers, inorganic aerogel fibers, and organic-inorganic hybrid aerogel fibers, have been fabricated successfully, suggesting the universality of the SGCT strategy, which not only provides a way for developing aerogel fibers with different components but also plays an irreplaceable role in promoting the upgrading of the fiber fields.

Populus species feature remarkable phytoremediation of cadmium (Cd) contamination. The influence of nitrogen (N) availability on Cd accumulation and tolerance in stems was investigated in a clone of Populus × euramericana. Secondary xylem development in stems was dramatically suppressed by the combined conditions of N deficiency and Cd exposure, but such suppression was partially alleviated by N application. Under adequate N condition, the Cd bioconcentration factor (BCF) in stems at moderate and high Cd exposures reached 3.07 and 0.91, respectively, whereas the Cd content in stems at high Cd exposure reached 164 μg Cd plant−1. However, Cd bioconcentration and accumulation in stems were sharply decreased due to N deficiency. The levels of phytohormones (abscisic acid, jasmonic acid, and salicylic acid) and antioxidants (free proline and peroxidase) in stems decreased in low N treatment because of poor tissue N concentration, thereby attenuating antioxidant defense and Cd tolerance. The decreased Cd tolerance and inhibited xylem development under low N condition led to the dramatic decrement of Cd accumulation in stems. Adequate N application increased the phytohormone and antioxidant levels in stems, thereby promoting antioxidant defense, as indicated by the low malondialdehyde (MDA) level. Moreover, both the improved antioxidant defense and appropriate N nutrient status contributed to xylem development. Consequently, the capacity for Cd bioconcentration and accumulation in Populus stems was promoted by N application, thereby facilitating the phytoextraction of Cd from Cd-contaminated soils.

The spoof localized surface plasmon (LSP) has been widely investigated but mostly with fixed multipole resonances. This Letter proposes a method to generate multipole resonances by adding a slit on the metallic ring of a complementary LSP. This slit theoretically introduces two new boundary conditions and new modes. To validate this approach, complementary LSPs with and without slits at three different angular positions are theoretically analyzed and numerically simulated. To validate and demonstrate the potential application of the proposed LSP structure, a bandpass filter (BPF) in a single-layer substrate is designed and measured by exciting the LSP with a slit on the metallic ring. The measured results show that by simply adding a slit, the BPF achieves a fractional bandwidth of 42.7% (2.5 GHz), for both | S 11 | < − 10 d B and | S 21 | within 1 dB variation. In the passband, a flat group delay between 0.57 ns and 0.75 ns is obtained. Moreover, the proposed structure features a low profile and a compact radius of 0.136 wavelength. By dynamically controlling slit/slits with varactors or diodes, the proposed structure is theoretically promising to be reconfigurable at microwave and even terahertz frequencies.

This paper proposes a compact model for chipless radio frequency identification (RFID) tag. This compact scalable model consists of capacitors, inductors, and resistors of which their values are directly described by the physical dimension of the chipless tag. Moreover, based on this compact model, radar cross section of chipless RFID tag is predicted, by analyzing polarizability based on surface current distribution in different modes. To validate the proposed model, a 5-bit chipless RFID tag based on high-impedance surface (HIS) is presented, with good agreement among modeled, simulated, and measured results. A wide range of physical parameters have also been validated to show the scalability. This compact scalable model of chipless RFID tag not only simplifies the tag design, but also provides an insight understanding of the HIS structure.

Fast eruption desorption ionization (FEDI) technique was developed for simple, rapid, and sensitive analysis of various compounds. The FEDI allows three analytical modes each with the unique characteristic. The results demonstrated that non-assisted eruption was suitable for stable and volatile compounds, energetic material (EM)-assisted for nonvolatile molecules especially metal compounds, and solvent-assisted eruption for fragile molecules. High-quality mass spectra with intact ions of analytes were obtained in positive and negative ion modes. Graphical Abstract ᅟ.

Significant genetic variations in N and P nutritional traits exist under combined conditions of soil P deficiency and N deposition and interactively contribute to growth benefits. Forest ecosystems encounter combined conditions of soil phosphorus (P) deficiency and atmospheric nitrogen (N) deposition. As such, determining genetic variations and interactions of N and P nutritional traits is important for silviculture. Low N (LN) and high N (HN) were combined with three P treatments in a pot experiment with five full-sib families of Masson pine (Pinus massoniana). The three P treatments are: low P in soil profile (low-P condition, LP), enriched P in topsoil and poor P in subsoil (medium–low-P condition, MLP), and high P in soil profile (high-P condition, HP). P acquisition was more significant for growth benefits than P utilization under LP. Growth response to N was higher under MLP and HP than that under LP because of more balanced plant N:P ratios in the two former conditions. Under HN, there were significant correlation between nitrogen acquisition efficiency (NAE) and phosphorus use efficiency (PUE) and they interactively contributed to growth promotion under N deposition. Significant genetic variations, as well as large heritability of growth and N and P nutritional traits, were detected under all N–P conditions. This finding indicated the feasibility of breeding families with improved nutrient efficiency under N–P conditions.

Knowledge of the allelic variation and epistatic interaction of vernalization genes is crucial to understanding seasonal growth habit and adaptability of genetic resources in cultivated (Hordeum vulgare) and wild (Hodeum spontaneum) barley. In this research, 1398 Chinese barley accessions were characterized with molecular markers for vernalization genes HvVRN1 and HvVRN2. Different combinations of haplotypes at these two vernalization genes were present at different frequencies in wild barley, landraces and modern cultivars. All of the HvVRN1 haplotypes except HvVRN1-7 (V 1-7 ) and HvVRN1-Hs (V 1-Hs ) were identified in the Chinese barley collection chosen for this study. Haplotype V 1-8 occurred at the highest frequency in spring V 1 alleles, and V 1-1 , V 1-4 and V 1-8 had broad geographic distributions in China. Haplotypes V 1-2 and V 1-3 are restricted to modern cultivars as they were introduced from exotic germplasm. A total of 18 HvVRN1/HvVRN2 multilocus haplotypes were identified. Most of the HvVRN1/HvVRN2 haplotypes were present in materials from the Yellow-Huai River Valley and Middle-Lower Yangtze Valley ecological zones, birthplace of Chinese farming. The predominant combinations in landraces were V 1-8 /V 2 and v 1 /V 2 , but v 1 /v 2 made up the highest proportion of modern cultivars. Haplotypes V 1-5 /v 2 , V 1-10 /V 2 and V 1-9 /V 2 showed a correlation with region. Our results confirmed the presence or absence of conserved regulatory elements and the length of the first intron of HvVRN1 plays a determinant role in the vernalization requirement of barley. This study provides useful information for breeding and utilization of Chinese barley germplasm.