大陆内部长余震序列及其对地震风险评估的启示

板块构造学说的最有力的特征之一,是已知的板块运动让我们对板块边界未来大地震的发震位置和平均复发间隔有更清晰的认识。然而,板块构造学说却不能预测板块内的地震何时何地发生,因为理想的板块内部是不会变形的。因此,板块内部的地震风险评估过于依靠如下假设:从有限的历史记录中得到的小地震发震位置能够反映出连续变形的地区,而变形将诱发未来大地震[1]。然而,本文将要说明的是,最近许多这样的小地震很可能是几百年前发生过的大地震的余震。文中将给出一个简单的模型,并由此模型得出:余震序列的长度和断层加载速率呈反比关系。发生在缓慢变形的大陆内部的余震序列,其持续时间与在快速加载的板块边界所观测到的典型的10年尺度余震序列相比要长得多。因为这些预测与观测结果相符,所以将大陆内部地震看作稳态地震活动的一般做法高估了目前地震活跃地区的地震危险性,而低估了其他地区的地震风险。

Design of Robotic Visual Servo Control Based on Neural Network and Genetic Algorithm

A new visual servo control scheme for a robotic manipulator is presented in this paper, where a back propagation （BP） neural network is used to make a direct transition from image feature to joint angles without requiring robot kinematics and camera calibration. To speed up the convergence and avoid local minimum of the neural network, this paper uses a genetic algorithm to find the optimal initial weights and thresholds and then uses the BP Mgorithm to train the neural network according to the data given. The proposed method can effectively combine the good global searching ability of genetic algorithms with the accurate local searching feature of BP neural network. The Simulink model for PUMA560 robot visual servo system based on the improved BP neural network is built with the Robotics Toolbox of Matlab. The simulation results indicate that the proposed method can accelerate convergence of the image errors and provide a simple and effective way of robot control.

Long aftershock sequences in North China and Central US: implications for hazard assessment in mid-continents

Because seismic activity within mid-continents is usually much lower than that along plate boundary zones, even small earthquakes can cause widespread con- cerns, especially when these events occur in the source regions of previous large earthquakes. However, these small earthquakes may be just aftershocks that continue for decades or even longer. The recent seismicity in the Tangshan region in North China is likely aftershocks of the 1976 Great Tangshan earthquake. The current earthquake sequence in the New Madrid seismic zone in central United States, which includes a cluster of M- 7.0 events in 1811-1812 and a number of similar events in the past millennium, is believed to result from recent fault reactivation that releases pre-stored strain energy in the crust. If so, this earthquake sequence is similar to aftershocks in that the rates of energy release should decay with time and the sequence of earthquakes will eventually end. We use simple physical analysis and numerical simulations to show that the current sequence of large earthquakes in the New Madrid fault zone is likely ending or has ended. Recognizing that mid-continental earthquakes have long aftershock sequences and complex spatiotemporal occur- rences are critical to improve hazard assessments.

Mantle anisotropy across the southwestern boundary of the Ordos block,North China

Located at the northeastern margin of the Tibetan plateau,the Ordos block is a stable tectonic unit in North China.With its active boundary fault zones,the Ordos block played an important role in the eastward extrusion mechanism of the Tibetan plateau.Peking University deployed a linear array of 15 portable broadband seismometers across the western Weihe graben during September 2005 to August 2006 and later a 2-D seismic array（Southwest Ordos Array） of 14 portable broadband seismometers during 2007-2008 at its southwestern boundary.Analyses of shear wave splitting of SKS and SKKS phases at these stations show that the fast directions trend ～110° with an average delay time of 0.9 s in the southwestern margin of the Ordos block.The agreement between the lithosphere deformation indicated by GPS data and Quaternary fault slip-rate observations and the mantle flow represented by shear wave splitting implies that accordant deformation patterns from lithosphere to asthenosphere in relation to the eastward extrusion of the Tibetan plateau could extend at least to 200 km depth.Spatial distribution of splitting polarization directions indicates that the mantle flow driven by the Tibetan plateau is blocked by the Ordos block and locally restricted in a narrow channel along the Qinling-Dabie fault zones between the Ordos block and Sichuan basin.

地震危险性图存在致命缺陷

《地壳构造物理学》（Tectonophysics）2012年第562—563卷刊登了题为《Why earthquake hazard maps often fail and what to do about it，为什么地震危险性图经常失败以及我们可以为此做些什么》的文章，该文指出，近代历史上3个最大、最致命的地震都发生在地震危险性图没有预测出大地震的地方，作者研究了危险性图无法预测这些地震的原因，探讨了改进危险性图的方法。

是假设有误还是运气不佳:地震危险性图为什么需要客观检验

近年来,许多破坏性大地震都发生在地震危险性图中明确标注为危险性相对较低的地方。令人惊奇的是,虽然许多国家都在使用这样的地震危险性图,但其效果却从未得到客观验证。

Active tectonics in Taiwan:insights from a 3-D viscous finite element model

Taiwan is a young orogenic belt with complex spatial distributions of deformation and earthquakes. We have constructed a three-dimensional finite element model to explore how the interplays between lithospheric struc- ture and plate boundary processes control the distribution of stress and strain rates in the Taiwan region. The model assumes a liberalized power-law rheology and incorporates main lithospheric structures; the model domain is loaded by the present-day crustal velocity applied at its bound- aries. The model successfully reproduces the main features of the GPS-measured strain rate patterns and the earth- quake-indicated stress states in the Taiwan region. The best fitting model requires the viscosity of the lower crust to be two orders of magnitude lower than that of the upper crust and lithospheric mantle. The calculated deviatoric stress is high in regions of thrust faulting and low in regions of extensional and strike-slip faulting, consistent with the spatial pattern of seismic intensity in Taiwan.

Crustal extension in North China since the Mesozoic: A numerical study

The ~1.8 billion years old North China Craton(NCC)has been thermally rejuvenated during the Mesozoic,experiencing two major phases of crustal extension and volcanism since then.The earlier phase of extension,lasted from middle Mesozoic to early Cenozoic,was widespread in eastern NCC and accompanied with extensive volcanism.The later phase of extension,started in late Cenozoic and is active today,has been localized around the Ordos block,a residual core of the NCC,with limited volcanism.Here we investigate the causes of the NCC extension using finite element method.Numerical results indicate that the diffuse and closely-spaced extension during Mesozoic and early Cenozoic requires a thin and weak lithosphere,which supports the notion of significant lithospheric thinning under the eastern NCC,perhaps by delamination or thermal erosion of the lithospheric root.The western NCC,including the Ordos block,was largely spared by this phase of extension.The late Cenozoic extension around the Ordos block is commonly attributed to the Indo-Asian collision and mantle flow under eastern NCC.Our numerical results show that,regardless of the causing mechanism,a relatively thick and strong lithosphere is needed for the localized extension in western NCC,and preexisting weak zones in the lithosphere is a necessary condition for localized rifting around the Ordos.This preexisting lithospheric weakness is most likely inherited from the amalgamation of the NCC basement ~1.8 billion years ago.The late Cenozoic circum-Ordos rifting thus illustrates the control of ancient continental structures on recent tectonics.

An integrated analysis of mRNA-miRNA transcriptome data revealed hub regulatory networks in three genitourinary cancers

Bladder,kidney,prostate and testicular carcinoma are the top four genitourinary cancers in China.Here we analyzed mRNA and miRNA expression profiles of carcinomas of the bladder(TCC),kidney(ccRCC)and testis(TGCT)to uncover their specific regulatory mechanisms.The gene expression profiles of GSE31617 were downloaded from GEO database,which contained 27 samples,including 10 TCC,7 TGCT and 10 ccRCC.Specific up-and downregulated differentially expressed genes(DEGs)and differentially expressed microRNAs(DEmiRNAs)of each cancer were selected and target genes of DEmiRNAs were predicted.Gene interaction network of the shared genes and target genes of DEmiRNAs of each cancer was predicted by STRING and constructed by Cytoscape.In each cancer,we build regulatory networks of hub genes selected and conducted GO analysis of enriched genes.Furthermore,we chose four hub genes(SALL4,RHEB,CDC42 and TNN)for survival analysis in OncoLnc database,and they all had effects on the survival rate of another genitourinary cancer-kidney renal clear cell carcinoma(KIRC).In conclusion,the present study indicated that the identified hub genes promote our understanding of molecular mechanisms underlying the development of three genitourinary cancers,and might be used as molecular targets and diagnostic biomarkers for the treatment of them.

New-onset primary Sjögren's syndrome following exposure to severe acute respiratory syndrome coronavirus 2: A retrospective cohort study

Background:Understanding the clinical implications of autoimmune manifestations associated with severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is essential to reduce its consequences. This study was aimed at determining the activities of new-onset primary Sjögren syndrome (pSS) since the emergence of SARS-CoV-2.Methods:This retrospective cohort study included data from 471 participants with dry mouths and eyes who had been attending Nanjing Drum Tower Hospital since December 2019. By April 2023, patients diagnosed with pSS were sequentially assigned to vaccinated group ( n = 24) or vaccinated and infected group based on exposure ( n = 20). Patients diagnosed with pSS within 3 months of vaccination against SARS-CoV-2 were assigned to a vaccinated group, and those who had been vaccinated and then developed pSS within 3 months of follow up after direct exposure to SARS-CoV-2 were assigned to a vaccinated and infected group. The controls comprised age- and sex-matched patients who had not been exposed to SARS-CoV-2 before December 2019 ( n = 21). We then compared data among the three groups. Results:The vaccinated and infected patients had more fever, malaise, splenomegaly, and weight loss before diagnosis and a higher European Alliance of Associations for Rheumatology Sjögren's syndrome disease activity index at the time of onset than the other two groups. Vaccinated patients had a higher frequency of anti-nuclear antibody (ANA) titers > 1:320 ( n = 12;50%) and anti-phospholipid antibodies (aPL) ( n = 7;29%) than the controls. The frequency of anti-Ro/SSA antibodies (13, 65%), ANA titers > 1:320 ( n = 16;80%), and aPLs ( n = 7;29%) ( n = 5;25%) were all significantly higher in vaccinated patients with infection than those in the controls. Higher doses of glucocorticoids, cyclosporin A, and tacrolimus were administered to the vaccinated and infected than the vaccinated and control groups ( p < 0.05, for all). Conclusions:Patients with new-onset pSS and a history of vaccination and SARS-CoV-2 infection might have more active disease. Further strengthening the assessment of people with a clear history of SARS-CoV infection and the monitoring of potential populations for autoimmune screening should not be overlooked.

利用接收函数研究六盘山地区地壳上地幔结构特征

利用六盘山地区宽频带流动地震台阵的远震体波记录,采用接收函数方法研究台阵下方的地壳上地幔结构,并采用接收函数振幅加权叠加方法对这一地区平均地壳厚度和泊松比进行估算.研究结果显示,青藏高原东北缘和鄂尔多斯的接触过渡带接收函数震相复杂,地壳变形强烈,青藏高原东北缘地壳平均厚度约为51.5km,六盘山下方地壳厚度在53.5km,鄂尔多斯西南缘地壳平均厚度约为50km,整个莫霍面呈下凹状.泊松比计算结果显示,六盘山东侧和西侧地壳泊松比值在正常范围内(0.25～0.26),六盘山下方的地壳泊松比值偏高(0.27～0.29),推测与地壳中存在部分熔融.泊松比值的横向变化,指示测线范围地壳物质组成和力学性质存在横向差异,反映在欧亚板块与印度板块碰撞作用影响下青藏高原下地壳物质存在向北东方向的流动.

Phylotranscriptomic insights into Asteraceae diversity,polyploidy,and morphological innovation

Biodiversity is not evenly distributed among relatedgroups,raising questions about the factors con-tributing to such disparities.The sunflower family(Asteraceae,>26,000 species)is among the largestand most diverse plant families,but its species di-versity is concentrated in a few subfamilies,pro-viding an opportunity to study the factors affectingbiodiversity.Phylotranscriptomic analyses here of244 transcriptomes and genomes produced a phy-logeny with strong support for the monophyly ofAsteraceae and the monophyly of most subfamiliesand tribes.This phylogeny provides a reference fordetecting changes in diversification rates and pos-sible factors affecting Asteraceae diversity,whichinclude global climate shifts,whole‐genome dupli-cations(WGDs),and morphological evolution.Theorigin of Asteraceae was estimated at~83 Mya,with most subfamilies having diverged before theCretaceous–Paleocene boundary.Phylotran-scriptomic analyses supported the existence of 41WGDs in Asteraceae.Changes to herbaceousnessand capitulescence with multipleflower‐like capitula,often with distinctflorets and scaly pappus/re-ceptacular bracts,are associated with multiple up-shifts in diversification rate.WGDs might have con-tributed to the survival of early Asteraceae byproviding new genetic materials to support mor-phological transitions.The resulting competitive ad-vantage for adapting to different niches would haveincreased biodiversity in Asteraceae.

Epidemiological and clinical characteristics of burns in the older person:a seven-year retrospective analysis of 693 cases at a burn center in south-west China

Background:Burns are one of the major traumas that may affect older individuals.The purpose of this study was to investigate the epidemiological and clinical characteristics of geriatric burns at a major center in south-west China.Methods:This retrospective study was conducted at the Institute of Burn Research,Southwest Hospital of Army Medical University between 2010 and 2016,and the data collected from medical records included admission date,age,gender,premorbid disease,burn etiology,injured anatomical location,burn area and depth,inhalation injury,number of surgeries,length of stay(LOS),clinical outcome,and medical cost.Results:Of the 693 older burn patients included,60.75%were male and 56.85%were aged 60–69 years.Burns peaked in December–March and June.Flamewas the most common cause of burns,making up 51.95%of all cases,and also dominated in the burn patients aged 60–69 years.Limbs were the most common anatomical sites of burns(69.41%),and the median total body surface area(TBSA)was 5%(interquartile range[IQR]:2%–15%).The percentage of the patients who underwent surgeries and number of surgeries significantly increased in the cases of contact burns,younger age and full-thickness burns.Six deaths resulted in a mortality of 0.9%.The median LOSwas 16 days(IQR:8–29 days),and the main risk factors were more surgeries,better outcomes,and full-thickness burns.The median costwas 20,228 CNY(IQR:10,457–46,581.5 CNY),and major risk factors included longer LOS,larger TBSA,and more surgeries.Furthermore,compared to the earlier data from our center,the proportion of older adults among all burns(7.50%vs.4.15%),proportion of flame burns(51.95%vs.33.90%),and mean age(69.05 years vs.65.10 years)were significantly higher,while the proportion of premorbidities(16.9%vs.83.9%),mortality(0.9%vs.7.5%)and median TBSA(5%vs.21%)were significantly lower.Conclusions:This study suggested that closer attention should be paid to prevent burn injuries in older people aged 60–69 years,especially males,regarding incidents in the summer and winter,and flame burns.Moreover,tailored intervention strategies based on related risk factors should be under special consideration.

Reduction of hexavalent chromium with scrap iron in a fixed bed reactor

The reduction of hexavalent chromium by scrap iron was investigated in continuous long-term fixed bed system. The effects of pH, empty bed contact time （EBCT）, and initial Cr（VI） concentration on Cr（VI） reduction were studied. The results showed that the pH, EBCT, and initial Cr（VI） concentration significantly affected the reduction capacity of scrap iron. The reduction capacity of scrap iron were 4.56, 1.51, and 0.57mg Cr（VI）-g1 Fe0 at pH 3, 5, and 7 （initial Cr（VI） concentration 4 mg.L 1, EBCT 2 min, and temperature 25℃）, 0.51, 1.51, and 2.85 mg Cr（VI）.g-I Fe0 at EBCTs of 0.5, 2.0, and 6.0rain （initial Cr（VI） concentration 4mg.L-1, pH 5, and temperature 25℃）, and 2.99, 1.51, and 1.01 mg Cr（VI）. gl Fe0 at influent concentrations of 1, 4, and 8 mg.L ^-1（EBCT 2 min, pH 5, and temperature 25℃）, respectively. Fe（total） concentration in the column effluent continuously decreased in time, due to a decrease in time of the iron corrosion rate. The fixed bed reactor can be readily used for the treatment of drinking water containing low amounts of Cr（VI） ions, although the hardness and humic acid in water may shorten the lifetime of the reactor, the reduction capacity of scrap iron still achieved 1.98 mg Cr6 ＋- g-~ Fe. Scanning electron micro- scope equipped with energy dispersion spectrometer and X-ray diffraction were conducted to examine the surface species of the scrap iron before and after its use. In addition to iron oxides and hydroxide species, iron-chromium complex was also observed on the reacted scrap iron.