Theories and applications of earthquake-induced gravity variation:Advances and perspectives

Earthquake-induced gravity variation refers to changes in the earth’s gravity field associated with seismic activities.In recent years,development in the theories has greatly promoted seismic deformation research,laying a solid theoretical foundation for the interpretation and application of seismological gravity monitoring.Traditional terrestrial gravity measurements continue to play a significant role in studies of interseismic,co-seismic,and post-seismic gravity field variations.For instance,superconducting gravimeter networks can detect co-seismic gravity change at the sub-micro Gal level.At the same time,the successful launch of satellite gravity missions(e.g.,the Gravity Recovery and Climate Experiment or GRACE)has also facilitated applied studies of the gravity variation associated with large earthquakes,and several remarkable breakthroughs have been achieved.The progress in gravity observation technologies(e.g.,GRACE and superconducting gravimetry)and advances in the theories have jointly promoted seismic deformation studies and raised many new research topics.For example,superconducting gravimetry has played an important role in analyses of episodic tremor,slow-slip events,and interseismic strain patterns;the monitoring of transient gravity signals and related theories have provided a new perspective on earthquake early warning systems;the mass transport detected by the GRACE satellites several months before an earthquake has brought new insights into earthquake prediction methods;the use of artificial intelligence to automatically identify tiny gravity change signals is a new approach to accurate and rapid determination of earthquake magnitude and location.Overall,many significant breakthroughs have been made in recent years,in terms of the theory,application,and observation measures.This article summarizes the progress,with the aim of providing a reference for seismologists and geodetic researchers studying the phenomenon of gravity variation,advances in related theories and applications,and future research directions in this discipline.

Aligned fibers enhance nerve guide conduits when bridging peripheral nerve defects focused on early repair stage

Nerve conduits enhance nerve regeneration in the repair of long-distance peripheral nerve defects. To help optimize the effectiveness of nerve conduits for nerve repair, we developed a multi-step electrospinning process for constructing nerve guide conduits with aligned nanofibers. The alignment of the nerve guide conduits was characterized by scanning electron microscopy and fast Fourier transform. The mechanical performance of the nerve guide conduits was assessed by testing for tensile strength and compression resistance. The biological performance of the aligned fibers was examined using Schwann cells, PC12 cells and dorsal root ganglia in vitro. Immunohistochemistry was performed for the Schwann cell marker S100 and for the neurofilament protein NF200 in PC12 cells and dorsal root ganglia. In the in vivo experiment, a 1.5-cm defect model of the right sciatic nerve in adult female Sprague-Dawley rats was produced and bridged with an aligned nerve guide conduit. Hematoxylin-eosin staining and immunohistochemistry were used to observe the expression of ATF3 and cleaved caspase-3 in the regenerating matrix. The recovery of motor function was evaluated using the static sciatic nerve index. The number of myelinated fibers, axon diameter, fiber diameter, and myelin thickness in the distal nerve were observed by electron microscopy. Gastrocnemius muscle mass ratio was also determined. The analyses revealed that aligned nanofiber nerve guide conduits have good mechanical properties and can induce Schwann cells, PC12 cells and dorsal root ganglia to aggregate along the length of the nanofibers, and promote the growth of longer axons in the latter two(neuronal) cell types. The aligned fiber nerve conduits increased the expression of ATF3 and cleaved caspase-3 at the middle of the regenerative matrix and at the distal nerve segment, improved sciatic nerve function, increased muscle mass of the gastrocnemius muscle, and enhanced recovery of distal nerve ultrastructure. Collectively, the results show that highly aligned nanofibers improve the performance of the nerve conduit bridge, and enhance its effectiveness in repairing peripheral nerve defects.

Time-space characteristics of viscoelastic post-seismic deformations corresponding to different rheology models

On a long time(>1 a)scale,the viscoelastic properties of mantle media significantly affect post-seismic deformation.The stress field disturbance in viscoelastic medium caused by fault slip gradually relax,and the relaxation process and its temporal-spatial characteristics are determined by the viscoelastic model.In this paper,we assume that the mantle media are types of common linear rheological models,i.e.,the Burgers body,the standard linear solid,and the Maxell body,and we calculate the dislocation Love number and Green function for a spherically symmetric,non-rotating,viscoelastic,and isotropic(SNRVEI)Earth model.The characteristics of the post-seismic relaxation deformations corresponding to the different models are compared.Our results show that for a short time period,the Burgers body and standard linear solid are similar;while for the long time period,the Burgers body and Maxwell body are similar.This suggests that the observations of post-seismic deformation on the surface have a great potential for the inversion of underground viscoelastic structures.However,the potential of using surface displacement to distinguish different rheological models is limited when the observation period is not long enough.

On the Sea Image in Dover Beach

Matthew Arnold’s Dover Beach skillfully uses the sea image to reveal the social condition of the Victorian people on the verge of spiritual collapse.The two opposing sea images at the beginning of the poem are a contrast between illusion and reality,thus triggering the contradiction between the Imaginary and the Real,which becomes an aesthetic symbol throughout the interpretation of the sea image and the writing of human spiritual world.From the time of Sophocles in ancient Greece to the Victorian period,the sea,as a mirror of the Imaginary,became a way for people to reflect on their suffering fate and harsh reality.Meanwhile,the powerful force of the sea drawing back pebbles contains the philosophical meaning of the Real world,which has the mysterious power to swallow everything and is difficult to be captured by the symbol language of the Symbolic society.The impact of the sea on the pebbles shows the contradiction between the Real and the Symbolic.The reinterpretation of the sea image in Dover Beach provides insight into reconciling the spirituality of people in the transition period to highly developed industrialization and modernization.

Protein microarray analysis of cytokine expression changes in distal stumps after sciatic nerve transection

A large number of chemokines,cytokines,other trophic factors and the extracellular matrix molecules form a favorable microenvironment for peripheral nerve regeneration.This microenvironment is one of the major factors for regenerative success.Therefore,it is important to investigate the key molecules and regulators affecting nerve regeneration after peripheral nerve injury.However,the identities of specific cytokines at various time points after sciatic nerve injury have not been determined.The study was performed by transecting the sciatic nerve to establish a model of peripheral nerve injury and to analyze,by protein microarray,the expression of different cytokines in the distal nerve after injury.Results showed a large number of cytokines were up-regulated at different time points post injury and several cytokines,e.g.,ciliary neurotrophic factor,were downregulated.The construction of a protein-protein interaction network was used to screen how the proteins interacted with differentially expressed cytokines.Kyoto Encyclopedia of Genes and Genomes pathway and Gene ontology analyses indicated that the differentially expressed cytokines were significantly associated with chemokine signaling pathways,Janus kinase/signal transducers and activators of transcription,phosphoinositide 3-kinase/protein kinase B,and notch signaling pathway.The cytokines involved in inflammation,immune response and cell chemotaxis were up-regulated initially and the cytokines involved in neuronal apoptotic processes,cell-cell adhesion,and cell proliferation were up-regulated at 28 days after injury.Western blot analysis showed that the expression and changes of hepatocyte growth factor,glial cell line-derived neurotrophic factor and ciliary neurotrophic factor were consistent with the results of protein microarray analysis.The results provide a comprehensive understanding of changes in cytokine expression and changes in these cytokines and classical signaling pathways and biological functions during Wallerian degeneration,as well as a basis for potential treatments of peripheral nerve injury.The study was approved by the Institutional Animal Care and Use Committee of the Chinese PLA General Hospital,China(approval number:2016-x9-07)in September 2016.

城市轨道交通工程中U型梁施工方法探讨与分析

U型梁(槽型梁)作为轨道交通工程双轨高架桥梁中的新式梁型结构,其在国内越来越多的轨道交通线路建设中都采用这一梁型。本文主要对宁句线工程U型梁的不同施工方法进行简要介绍,比较该工程中现浇法和预制法在施工顺序、施工条件、施工难度、环境影响及经济性方面的优劣,从而得出各自的适用范围,为以后轨道交通工程中U型梁的设计选型和施工方法选择提供参考。

In Situ Analysis of Tobacco Leaves Based on Microwave Plasma Torch Desorption Ionization Mass Spectrometry

Tobacco is an important economic crop worldwide.Tobacco leaves contain a large number of natural products.Therefore,the analysis of tobacco composition is crucial for the control of tobacco safety and quality assessment.Microwave plasma torch desorption ionization mass spectrometry(MPT-MS) is an emerging ambient mass spectrometry(AMS) technique that can be used for rapid real-time analysis of s amples without pretreatment.Our work focuses on the chemical composition analysis of tobacco using MPT-MS,and 14 compounds were detected in green flue-cured tobacco leaves,while 30 compounds were detected in cured flue-cured tobacco leaves,which confirms that curing can enhance the flavor of cigarettes.Furthermore,we successfully in situ identified characteristic fragment ions of α/β-CBD(α/β-cembranoids),an important aroma compound in tobacco by MPT-MS.The results demonstrate the capability of MPT-MS for in situ analysis of tobacco components and its potential for evaluating tobacco quality.

Uniform Asymptotic Normality of the Matrix-variate Beta-distribution

With the upper bound of Kullback-Leibler distance between a matrix variate Beta-distri- bution and a normal distribution, this paper gives the conditions under which a matrix-variate Beta- distribution will approach uniformly and asymptotically a normal distribution.

Clinical characteristics and effectiveness of antiviral agents in hospitalized children with infectious mononucleosis in China:A multicenter retrospective study

Importance:The clinical characteristics of infectious mononucleosis(IM)in Chinese children have not been evaluated in multicenter studies,and the effectiveness of antiviral treatment are controversial.Objective:To investigate the clinical characteristics of Chinese children with IM and current status of antiviral therapy for affected patients.Methods:Hospitalized patients with IM were enrolled between 2018 and 2020 in five children’s hospitals in China.The clinical characteristics were compared among four age groups:<3 years,3-<6 years,6-<10 years,and≥10 years.The clinical characteristics of IM and effectiveness of antiviral therapy were compared among patients receiving acyclovir(ACV),ganciclovir(GCV),and no antiviral therapy(i.e.,non-antiviral group).Results:In total,499 patients were analyzed;most patients were 3-<6 years of age.The most common symptoms and signs included fever(100%),lymphadenopathy(98.6%),pharyngitis(86.4%),eyelid edema(76.8%),and snoring(72.9%).There were significant differences in rash,hepatomegaly,and liver dysfunction among the four age groups.Patients aged<3 years had a lower incidence of liver dysfunction and a higher incidence of rash.Among the 499 patients,50.1%were treated with GCV,26.3%were treated with ACV,and 23.6%received no antiviral therapy.Compared with the non-antiviral group,patients in the ACV and GCV groups had longer durations of fever(P<0.001).There were no significant differences in the incidences of complications among the three treatment groups.Interpretation:The incidence of IM in Chinese children peaked at 3-<6 years of age.Clinical features of IM varied according to age.Patients receiving antiviral therapy exhibited more serious clinical manifestations than did patients without antiviral therapy.The effectiveness of antiviral therapy for IM requires further analysis.

Enhanced Offset Averaging Technique for Flash ADC Design

This paper presents a new combined AC/DC-coupled output averaging technique for input amplifier design of flash analog-to-digital converters （ADC）. The new offset averaging design technique takes full advantage of traditional DC-coupled resistance averaging and AC-coupled capacitance averaging techniques to minimize offset-induced ADC nonlinearities. Circuit analysis allows selection of optimum resistance and capacitance averaging factors to achieve maximum offset reduction in ADC designs. The new averaging method is verified in designing a 4 bit 1 Gs/s flash ADC that is implemented in foundry 0.13 μm CMOS technology.

Whole-Chip ESD Protection Design for RF and AMS ICs

As integrated circuits （IC） technologies advance into very-deep-sub-micron （VDSM）, electrostatic discharge （ESD） failure becomes one of the most devastating IC reliability problems and on-chip ESD protection design emerges as a major challenge to radio frequency （RF）, analog, and mixed-signal （AMS） IC designs. This paper reviews key design aspects and recent advances in whole-chip ESD protection designs for RF/AMS IC applications in CMOS technologies.

ESD-Induced Noise to Low Noise Amplifier Circuits in BiCMOS

Electrostatic discharge （ESD） induced parasitic effects have serious impacts on performance of radio frequency （RF） integrated circuits （IC）. This paper discusses a comprehensive noise analysis procedure for ESD protection structures and their negative influences on RF ICs. Noise figures （NFs） of commonly used ESD protection structures and their impacts on a single-chip 5.5 GHz low-noise amplifier （LNA） circuit were depicted. A design example in 0.18 μm SiGe BiCMOS was presented. Measurement results confirm that significant noise degradation occurs in the LNA circuit due to ESD-induced noise effects. A practical design procedure for ESD-protected RF ICs is provided for real-world RF IC optimization.