马来酸二丁酯接枝高密度聚乙烯及其在粘接树脂中的应用

以马来酸二丁酯(DBM)为单体、无味过氧化二异丙苯(BIBP)为引发剂、高密度聚乙烯(HDPE)为基体树脂,通过反应挤出制备相容剂HDPE-g-DBM。研究单体和引发剂浓度、配比、反应温度及螺杆转速对相容剂熔体质量流动速率(MFR)和接枝率(GD)的影响。通过复配相容剂和聚烯烃树脂,研究其在粘接树脂中的应用。采用熔体流动速率仪、傅里叶红外光谱等对相容剂进行了表征和分析;使用万能试验机和热变形维卡软化点试验机检测粘接树脂力学性能和维卡软化点。结果表明,在BIBP引发作用下,DBM可以接枝到HDPE上,当DBM的质量分数为2%、BIBP的质量分数为0.14%时,相容剂的MFR为2.07 g/10 min、GD为1.9%;粘接树脂中加入20%的相容剂后,粘接树脂各项性能均能符合给水用钢丝网增强聚乙烯复合管道对于粘接树脂的参数要求。

Multitaper spectral method to estimate the elastic thickness of South China: Implications for intracontinental deformation

The effective elastic thickness （Te） represents the thickness of the elastic layer or the flexural rigidity of the lithosphere, the equivalent of which can be calculated from the spectral analysis of gravity and topographic data. Studies of Te have profound influence on intracontinental deformation, and coupling of the tectonic blocks. In this paper, we use the multitaper spectral estimation method to calculate the coherence between Bouguer gravity and topography data, and to obtain the Te map of South China. Through the process of correction, we discuss the relationships of Te versus heat flow, and Te versus seismicity. The results show that Te distribution of South China is affected by three factors：the original age, which controls the basic feature;the Mesozoic evolution, which affects the Te distribution;and the neotectonic movement, which shaped the final distribution. The crust age has a positive correlation with the first-order Te distribution;thus the Yangtze Craton has a relatively higher Te （about 50 km） whereas the Te in Cathaysia block is only 10e20 km. By analysis and comparison among the tectonic models of South China, the Te distribution can be well explained using the flat-subduction model. As is typical with neotectonics, the region with a higher heat flow is related with a lower Te. The seismicity does not have a clear relationship with Te, but the strong seismicity could cause a low Te. Seismogenic layer （Ts） has a similar trend as Te in the craton, whereas in other areas the relationship is complex.

Seismic traveltime inversion of 3D velocity model with triangulated interfaces

Seismic traveltime tomographic inversion has played an important role in detecting the internal structure of the solid earth. We use a set of blocks to approximate geologically complex media that cannot be well described by layered models or cells. The geological body is described as an aggregate of arbitrarily shaped blocks,which are separated by triangulated interfaces. We can describe the media as homogenous or heterogeneous in each block. We define the velocities at the given rectangle grid points for each block,and the heterogeneous velocities in each block can be calculated by a linear interpolation algorithm. The parameters of the velocity grid positions are independent of the model parameterization,which is advantageous in the joint inversion of the velocities and the node depths of an interface. We implement a segmentally iterative ray tracer to calculate traveltimes in the 3D heterogeneous block models.The damped least squares method is employed in seismic traveltime inversion,which includes the partial derivatives of traveltime with respect to the depths of nodes in the triangulated interfaces and velocities defined in rectangular grids. The numerical tests indicate that the node depths of a triangulated interface and homogeneous velocity distributions can be well inverted in a stratified model.

Upper crustal structure under Jingtai–Hezuo profile in Northeastern Tibet from topography-dependent eikonal traveltime tomography

The Northeastern Tibetan plateau records Caledonian Qilian orogeny and Cenozoic reactivation by continental collision between the Indian and Asian plates. In order to provide the constraint on the Qilian orogenic mechanism and the expansion of the plateau,wide-angle seismic data was acquired along a 430 km-long profile between Jingtai and Hezuo. There is strong height variation along the profile,which is dealt by topography flattening scheme in our crustal velocity structure reconstruction. We herein present the upper crustal P-wave velocity structure model resulting from the interpretation of first arrival dataset from topography-dependent eikonal traveltime tomography. With topography flattening scheme to process real topography along the profile,the evenness of ray coverage times of the image area（upper crust）is improved,which provides upper crustal velocity model comparable to the classic traveltime tomography（with model expansion scheme to process irregular surface）. The upper crustal velocity model shows zoning character which matcheswith the tectonic division of the Qaidam-Kunlun-West Qinling belt,the Central and Northern Qilian,and the Alax blocks along the profile. The resultant upper crustal P-wave velocity model is expected to provide important base for linkage between the mapped surface geology and deep structure or geodynamics in Northeastern Tibet.

The gravity and isostatic Moho in North China Craton and their implications to seismicity

The Bouguer gravity is the combination of field sources in different depths. Based on the multi-scale analysis of the Bouguer gravity,we can get the gravity anomaly caused by the Moho undulation. This study presents the various orders of approximation of gravity anomaly in North China Craton（NCC）,the possible source depths with radial logarithmic power spectrum,and the relationship between the deep structure and gravity anomaly. Furthermore,we discuss the isostatic compensation about the Moho depth from gravity and deep seismic sounding profiles（DSS）. The results show that：（1） the fourth approximation could have resulted from the Moho undulation,（2） in contrast to the isostatic Moho,the inverted gravity Moho and the DSS Moho show that most of NCC has been isostatically compensated,and（3） the isostatic compensation rate has some close relation to the seismicity.

Modeling of Rayleigh wave dispersion in Iberia

Phase and group velocities of 15-70 s Rayleigh waves propagating across the Iberian Penin- sula have been transformed into local dispersion curves by linear inversion of travel times. The procedure permits that the waveform dispersion to be obtained as a continuous period-dependent velocity function at grid points belonging to the area probed by the waves, thus providing phase- and group-velocity contour maps for several periods within the interval of interest. The regionalization process rests on a homoge- neous initial data set in which the number of observations remains almost constant for all periods of reference. Damped least-squares inversion of the local dispersion curves for shear-wave velocity structure is performed to obtain depth-dependent S-wave velocity profiles at the grid points covering the model region. The reliability of the results should improve significantly owing to the use of phase and group velocities simultaneously. On this basis, we have built horizontal depth sections that give an updated view of the seismic velocity structure of the peninsula at lithospheric and upper mantle depths （20--200 km）. After averaging all the pure-path S-wave velocities previously determined at each grid point, the velocity- depth models so obtained for major tectonic units allow the comparison between the Hercynian basement and other areas of Mesozoic folding and Tertiary hasins

Single-cell transcriptomes provide insights into expansion of glial cells in Bombyx mori

The diversity of cell types in the brain and how these change during different developmental stages,remains largely unknown.The life cycle of insects is short and goes through 4 distinct stages including embryonic,larval,pupal,and adult stages.During postembryonic life,the larval brain transforms into a mature adult version after metamorphosis.The silkworm,Bombyx mori,is a lepidopteran model insect.Here,we characterized the brain cell repertoire of larval and adult B.mori by obtaining 50708 single-cell transcriptomes.Seventeen and 12 cell clusters from larval and adult brains were assigned based on marker genes,respectively.Identified cell types include Kenyon cells,optic lobe cells,monoaminergic neurons,surface glia,and astrocyte glia.We further assessed the cell type compositions of larval and adult brains.We found that the transition from larva to adult resulted in great expansion of glial cells.The glial cell accounted for 49.8%of adult midbrain cells.Compared to flies and ants,the mushroom body kenyon cell is insufficient in B.mori,which accounts for 5.4%and 3.6%in larval and adult brains,respectively.Analysis of neuropeptide expression showed that the abundance and specificity of expression varied among individual neuropeptides.Intriguingly,we found that ion transport peptide was specifically expressed in glial cells of larval and adult brains.The cell atlas dataset provides an important resource to explore cell diversity,neural circuits and genetic profiles.

Two dehydroecdysone reductases act as fat body-specific 20E catalyzers in Bombyx mori

Periodic post-embryonic changes in insects, including growth, development and metamorphosis, are strictly controlled by many compounds, including steroid hormones. The biosynthesis and clearance of 20-hydroxyecdysone (20E), the major active form of the insect steroid hormone ecdysone, result in titer fluctuations that help control insect development. The inactivation of 20E in the silkworm Bombyx mori is highly tissue-specific, with CYP18A1 and ecdysone oxidase controlling 20E inactivation specifically in the mid-silk gland and midgut, respectively. Here, we characterized silkworm 3-dehydroecdysone 3α reductase (Bm3DE3α) and 3-dehydroecdysone 3β reductase (Bm3DE3β), two enzymes involved predominantly in the C-3-mediated catalysis of 20E in fat bodies. The ubiquitous and silk gland-specific overexpression of Bm3DE3α decreased the 20E titer, resulting in larval lethality and larval–pupal transition failure, respectively. In contrast, the ubiquitous and mid-silk gland-specific overexpression of Bm3DE3β increased the 20E titer, resulting in larval growth delays and lethality at the mid-fifth larval stage, respectively. Thus, Bm3DE3α and Bm3DE3β mediate fat body-specific steroid hormone metabolism in B. mori, indicating that highly diversified 20E metabolism-related mechanisms exist in different insect species.

A CCCH zinc finger gene regulates doublesex alternative splicing and male development in Bombyx mori

Recent identification of a Piwi-interacting RNA(piRNA)-initiated sex determination cascade in the silkworm,Bombyx mori,provides novel insights into high diversity of insect sex determination pathways.In this system,the W-chromosome-derived Fem piRNA is the primary sex determination signal.A CCCH-type zinc finger gene Masculinizer(Masc),which is targeted by Fem piRNA-PIWI complex in female animals,is indispensable for male-specific splicing of B.mori doublesex(Bmdsx).Although many genes involved in this cascade have been identified,the regulatory mechanisms of silk-worm sex determination remain to be elucidated.Here we show that another CCCH-type zinc finger gene,Bmznf-2,is a masculinization factor in B.mori.Bmznf-2 shows testisabundant expression and loss of Bmznf-2 function via clustered regularly interspaced short palindromic repeats 1 single-guide RNA-mediated mutagenesis results in feminized differentiation and appearance of the female-specific splicing variants of Bmdsx transcripts in males.In contrast,there is no phenotypic consequence in mutant females.In mutant males,relative messenger RNA expression levels of female-dominant genes such as vitellogenin and sex-specific storage protein I are significantly clevated while several male-dominant genes are significantly down-regulated.Furthermore,male mutants show delayed developmental timing,smaller body sizes of larvae and malformation of moth wings.Our data thus reveal that Bmznf-2 plays an indispensable role in silkworm male sexual differentiation.

Boundary Integral Modelling of Elastic Wave Propagation in Multi-Layered 2DMedia with Irregular Interfaces

We present a semi-analytic method based on the propagation matrix formulation of indirect boundary element method to compute response of elastic(and acoustic)waves in multi-layered media with irregular interfaces.The method works recursively starting from the top-most free surface at which a stress-free boundary condition is applied,and the displacement-stress boundary conditions are then subsequently applied at each interface.The basic idea behind this method is the matrix formulation of the propagation matrix(PM)or more recently the reflectivity method as wide used in the geophysics community for the computation of synthetic seismograms in stratifiedmedia.The reflected and transmittedwave-fields between arbitrary shapes of layers can be computed using the indirect boundary element method(BEM,sometimes called IBEM).Like any standard BEM,the primary task of the BEM-based propagation matrix method(thereafter called PM-BEM)is the evaluation of element boundary integral of the Green’s function,for which there are standard method that can be adapted.In addition,effective absorbing boundary conditions as used in the finite difference numerical method is adapted in our implementation to suppress the spurious arrivals from the artificial boundaries due to limited model space.To our knowledge,such implementation has not appeared in the literature.We present several examples in this paper to demonstrate the effectiveness of this proposed PM-BEM for modelling elastic waves in media with complex structure.