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A genetic algorithm was employed as a novel method to determine the best combination of materials for a double-layer electromagnetic shielding composite with good electromagnetic wave absorption efficiency at high frequencies from numerous magnetic materials. A carbonyl iron soft magnetic composite and a flaky FeNi soft magnetic composite were used to form the double-layer composite. The reflection and transmission parameters of the double-layer composite were measured using a vector network analyzer. The electromagnetic shielding effectiveness (SE) of the double-layer composite was calculated and analyzed. The double-layer composite was composed of two shielding materials with different electromagnetic parameters and demonstrated an excellent electromagnetic SE greater than 20 dB above 4 GHz; the ratio of the absorption efficiency (SEA) to SE (SEA/SE) was greater than 0.95, which indicates that more than 95% of the electromagnetic waves at high frequencies were attenuated by the shielding material, rather than being scattered into the surrounding environment. The double-layer composite exhibits excellent performance toward high electromagnetic waves absorption during the EMI shielding process.

In order to fracture shale gas reservoir with carbon dioxide as the working fluid, laboratory experiments were firstly conducted to measure the influence of carbon dioxide immersion on shale rock’s properties, and then the coupling mechanism between stress and seepage during hydraulic fracturing was simulated based on cohesive zone model. The fracturing ability of carbon dioxide and water was also compared under the same working conditions, and finally sensitivity analysis (including elastic modulus of shale, filtration coefficient, pump rate and viscosity of carbon dioxide) were conducted based on field application. The results show that, the elastic modulus of shale increased by 32.2%, the Poisson's ratio decreased by 40.3% and the compressive strength decreases by 22.9% after geothermal reaction with carbon dioxide under 30 MPa and 335.15 K for 2 hours. Compared with water fracturing, carbon dioxide fracturing induces longer fracture (increased by 25.3%) and narrower fracture (decreased to 40.8%). The fracture tends to get longer and narrower with increasing elastic modulus of shale. As filtration coefficient increases, the maximum width of fracture decreases significantly, whereas the length changes little. Both the length and maximum width of fracture increase with increasing pump rate, however the changing rate of length tends to decrease. The influence of viscosity of carbon dioxide on both fracture width and length is negligible, which validates the stable feasibility of carbon dioxide fracturing in different formation conditions.

To satisfy impedance matching at low frequencies and obtain high microwave absorption performance, easy-plane anisotropy Fe–Si powders coated with SiO2 were produced by a ball milling technique and a chemical deposition method. Then, a scanning electron microscope, a transmission electron microscope, an X-ray photoelectron spectrometer, an X-ray diffractometer, a Mossbauer spectrometer, a vibrating sample magnetometer, and a vector network analyzer were used to characterize the samples. Compared to easy-plane anisotropy Fe–Si powders without surface modification, the dielectric constant of easy-plane anisotropy Fe–Si powders with SiO2 coating decreased dramatically and the microwave absorption performance was improved significantly. The reflection loss peak reached − 10 dB when the thickness was 1.4 mm and even reached − 34 dB when the thickness was 4.5 mm, exhibiting great potential for application in thin absorbers working in the frequency range of 0.1–4 GHz. In addition, the microwave absorption performance at oblique incidence was also investigated. A reflection loss peak of − 30 dB was obtained when the incident angle was 30°, and a reflection loss peak of more than − 10 dB can still be obtained even when the incident angle was 80°. The results show that the easy-plane anisotropy Fe–Si powders with SiO2 coating still possess high microwave absorption performance at oblique incidence.

The Cambrian Period is the first period of the Phanerozoic Eon and witnessed the explosive appearance of the metazoans, representing the beginning of the modern earth-life system characterized by animals in contrary to the Precambrian earth-life system dominated by microbial life. However, understanding Cambrian earth-life system evolution is hampered by regional and global stratigraphic correlations due to an incomplete chronostratigraphy and consequent absence of a high-resolution timescale. Here we briefly review the historical narrative of the present international chronostratigraphic framework of the Cambrian System and summarize recent advances and problems of the undefined Cambrian stage GSSPs, in particular we challenge the global correlation of the GSSP for the Cambrian base, in addition to Cambrian chemostratigraphy and geochronology. Based on the recent advances of the international Cambrian chronostratigraphy, revisions to the Cambrian chronostratigraphy of China, which are largely based on the stratigraphic record of South China, are suggested, and the Xiaotanian Stage is newly proposed for the Cambrian Stage 2 of China. We further summarize the integrative stratigraphy of South China, North China and Tarim platforms respectively with an emphasis on the facies variations of the Precambrian-Cambrian boundary successions and problems for identification of the Cambrian base in the different facies and areas of China. Moreover, we discuss stratigraphic complications that are introduced by poorly fossiliferous dolomite successions in the upper Cambrian System which are widespread in South China, North China and Tarim platforms.

Co@C nanofibers have been prepared by an electrospinning technique. Uniform morphology of the nanofibers and good dispersion of the magnetic cobalt nanoparticles in the carbon fiber frame were confirmed by field-emission scanning electron microscopy and high-resolution transmission electron microscopy. The electromagnetic parameters of a composite absorber composed of Co@C nanofibers/paraffin were measured from 2 GHz to 15 GHz. The electromagnetic wave absorption properties were simulated and investigated in the case of normal and oblique incidence. In the normal case, the absorber achieved absorption performance of − 40 dB at 7.1 GHz. When the angle of incidence was increased to 60°, the absorption effect with reflection loss (RL) exceeding − 10 dB could still be obtained. These results demonstrate that the reported Co@C nanofiber absorber exhibits excellent absorption performance over a wide range of angle of incidence.

In order to further study on radiation of a moving electron in poloidal magnetized plasma (PMP), theoretical analysis and simulation calculation of Cherenkov radiation (CR) under the condition of an accelerated electron beam in PMP are respectively presented in this paper. Through analysis of dielectric tensor in poloidal magnetized plasma with uniformly accelerated electron and description of beam-wave interaction in PMP by Maxwell’s equations, radiation mechanism of uniformly accelerated electron CR in PMP is described. Then eigenvalue and radiation condition are respectively obtained. Moreover, dispersion relation of radiation wave is also deduced through analysis of eigenvalues. At the same time, through analysis of effect that cyclotron frequency and plasma frequency have on eigenvalue, it is discovered that plasma frequency has great effect on not only p1 mode but also p2 mode, but cyclotron frequency only affects p2 mode. Finally, through simulation calculation, dispersion curves of both p1 mode and p2 mode are presented. Through comparing to the case of uniform moving electrons, the radiation conditions of the accelerated electrons are more relaxed, more prone to generate radiation. The theoretical analysis and simulation calculation can provide for further research of the radiation microwave in PMP.

Despite rapid progresses in the genome-editing field, in vivo simultaneous overexpression of multiple genes remains challenging. We generated a transgenic mouse using an improved dCas9 system that enables simultaneous and precise in vivo transcriptional activation of multiple genes and long noncoding RNAs in the nervous system. As proof of concept, we were able to use targeted activation of endogenous neurogenic genes in these transgenic mice to directly and efficiently convert astrocytes into functional neurons in vivo. This system provides a flexible and rapid screening platform for studying complex gene networks and gain-of-function phenotypes in the mammalian brain.

We have synthesized thin Fe3O4 microflakes by a simple hydrothermal method and prepared Fe3O4 microflake–paraffin composites without and with magnetic orientation using the method of simple ultrasonic mixing and rotating samples in a magnetic field. X-ray diffractometer, Mossbauer spectrum, scanning electron microscope and vibrating sample magnetometer were used to characterize the samples. The complex permittivity and permeability of Fe3O4 microflake–paraffin composites without and with magnetic orientation were measured in the frequency range of 0.1–18 GHz by a vector network analyzer using a coaxial method. The reflection loss (RL) was calculated by the measured electromagnetic parameters using transmission line theory. The measurement of electromagnetic parameters shows that magnetic orientation makes the complex permittivity and permeability increase. The calculated RL shows that the Fe3O4 microflake–paraffin composite with magnetic orientation has enhanced microwave absorption properties in the frequency range of 1–3 GHz and the thickness range of 2.9–3.5 mm, indicating that the Fe3O4 microflake–paraffin composite with magnetic orientation is a promising thin microwave absorption material in the L-S band.

The cell divisions cycle 42 (Cdc42) gene has been characterized in the fungi, such as Candida albicans, Penicillium marneffei, and Wangiella (Exophiala) dermatitidis, which plays important roles during growth and development. The partial cDNA sequence of Cdc42 of Fonsecaea monophora (F. monophora), designated FmCdc42, was obtained using degenerate primers based on the conserved domain of the other fungi Cdc42. Then the complete cDNA sequence of FmCdc42 was obtained by 5' and 3' RACE. The full-length cDNA is 1,510 bp in size which had an open reading frame (ORF) of 582 bp, encoding 193 amino acid residues. The predicted molecular mass of FmCdc42 is 21.5 kDa with an estimated theoretical isoelectric point of 5.67. The deduced amino acid sequence of FmCdc42 shows 99% identity to that of Wangiella (Exophiala) dermatitidis. 5 exons and 4 introns are identified within the 1,617 bp FmCdc42 genomic DNA sequence of F. monophora. The ORF could be subcloned into the pCDNA6/myc-His B expression vector. The recombinant protein about 27.5 kD infusion protein had high expression level in Vero cells with SDS-PAGE and Western blot analysis. Quantitative real time RT-PCR revealed that FmCdc42 was the highest expression in the sclerotic bodies' stage compared with that in the mycelia and conidia stages, which indicated that the FmCdc42 may be involved in formation of F. monophora sclerotic bodies.

The controversy generated by the identification of phosphatized microfossils from the Doushantuo Formation in southern China as the embryos of early animals continues. A recent suggestion, that the roughly 600-million-year-old microfossils may be giant sulphur-oxidizing bacteria similar to the extant Thiomargarita, has been put to the test and found wanting — at least for some of the specimens. New observations reveal that some of the embryo-like fossils are found within elaborate organic vesicles called acritarchs, consistent with a reproductive strategy known as embryonic diapause, in which early embryos enter a dormant 'egg cyst' state. This suggests that these organisms were eukaryotes. Further arguments against the 'giant bacteria' explanation are presented online in a Brief Communications Arising contribution, which includes the suggestion that bacteria-like microfossils may have been stripped of their outer layers by the vagaries of fossil formation and preservation. Phosphatized microfossils in the Ediacaran (635–542 Myr ago) Doushantuo Formation, south China, have been interpreted as the embryos of early animals1,2,3,4. Despite experimental demonstration that embryos can be preserved5, microstructural evidence that the Doushantuo remains are embryonic6 and an unambiguous record of fossil embryos in Lower Cambrian rocks7, questions about the phylogenetic relationships of these fossils remain. Most recently, some researchers have proposed8 that Doushantuo microfossils may be giant sulphur-oxidizing bacteria comparable to extant Thiomargarita sp. Here we report new observations that provide a test of the bacterial hypothesis. The discovery of embryo-like Doushantuo fossils inside large, highly ornamented organic vesicles (acritarchs) indicates that these organisms were eukaryotic, and most probably early cleavage stage embryos preserved within diapause egg cysts. Large acanthomorphic microfossils of the type observed to contain fossil embryos first appear in rocks just above a 632.5 ± 0.5-Myr-old ash bed9, suggesting that at least stem-group animals6 inhabited shallow seas in the immediate aftermath of global Neoproterozoic glaciation.