Extraction of transient signal from GPS position time series by employing ICA

Transient deformation,such as post-seismic slip,slow slip and pre-seismic slip events,is a limited lowfrequency deformation that can last for hours to months,in contrast to a sudden slip on a fault caused by earthquakes.Continuous Global Positioning System(CGPS),one of the most common geodetic techniques for continuously monitoring crustal deformation,is capable of capturing transient deformation signals.A critical point in characterizing transient deformation signals is the development of extracting and deciphering transient deformation signals from a huge and messy data set of position time series.Principal Component Analysis(PCA),one of the data-driven methods,has been employed to derive transient deformation signals from position time series combing with Kalman filtering.Independent Component Analysis(ICA)performs well in recovering and separating the sources of observed data,however,it is rarely used in extracting transient deformation signals.We aim to decompose the transient deformation signals from the daily GPS observation deployed in Akutan Island from 2007 to 2015 with the ICA method and obtain the spatiotemporal responses to the source signals of transient deformation.Our results indicate that ICA method can also characterize effectively transient deformation signals spatially and temporally.Additionally,the independent relationship between sources obtained by ICA allows for flexibility in linearly combining different sources.

Coseismic vertical deformation of the M_S8.0 Wenchuan earthquake from repeated levelings and its constraint on listric fault geometry

The devastating MS8.0 Wenchuan earthquake ruptured two large parallel thrust faults along the middle segment of the Longmenshan thrust belt.Preseismic and postseismic leveling data indicated the hanging wall of the YingxiuBeichuan-Nanba thrust fault mainly presented coseismic uplift with respect to the reference point at Pingwu county town, and the observed maximum uplift of 4.7 m is located at Beichuan county(Qushan town)which is about 100 m west of the fault scarp.The foot wall of the Yingxiu-Beichuan-Nanba thrust fault mainly showed subsidence with maximum subsidence of 0.6 m near the rupture.By employing a listric dislocation model,we found that the fault geometry model of exponential dip angleδ=88°×[1-exp(-9/h)]with depth of 18 km and uniform thrust-slip of 5.6 m could fit the observed coseismic vertical deformation very well,which verifies the listric thrust model of the Longmenshan orogenic zone.

浆细胞性乳腺炎合并导管内癌一例

根据2020年世界卫生组织报告,乳腺癌已成为全球新发癌症病例中占比最高的恶性肿瘤,约占新发病例总数的11.7%[1]。浆细胞性乳腺炎(plasma cell mastitis,PCM),又称乳腺导管扩张症,是最常见的非哺乳期乳腺炎,好发于30~50岁的非哺乳期妇女,约占乳房良性病变的4%~5%,且发病率呈上升、年轻化趋势[2]。而PCM治疗周期较长,并发乳腺癌的情况容易被忽略,这可能延误恶性疾病的治疗。重庆医科大学附属第二医院收治一例浆细胞性乳腺炎合并导管内癌患者,现结合相关文献报告如下。

Environmental impact and health risk assessment of volatile organic compound emissions during different seasons in Beijing

Volatile organic compounds(VOCs)are major contributors to air pollution.Based on the emission characteristics of 99 VOCs that daily measured at 10 am in winter from 15 December 2015 to 17 January 2016 and in summer from 21 July to 25 August 2016 in Beijing,the environmental impact and health risk of VOC were assessed.In the winter polluted days,the secondary organic aerosol formation potential(SOAP)of VOC(199.70±15.05 mg/m^3)was significantly higher than that on other days.And aromatics were the primary contributor(98.03%)to the SOAP during the observation period.Additionally,the result of the ozone formation potential(OFP)showed that ethylene contributed the most to OFP in winter(26.00%and 27.64%on the normal and polluted days).In summer,however,acetaldehyde was the primary contributor to OFP(22.00%and 21.61%on the normal and polluted days).Simultaneously,study showed that hazard ratios and lifetime cancer risk values of acrolein,chloroform,benzene,1,2-dichloroethane,acetaldehyde and 1,3-butadiene exceeded the thresholds established by USEPA,thereby presenting a health risk to the residents.Besides,the ratio of toluene-to-benzene indicated that vehicle exhausts were the main source of VOC pollution in Beijing.The ratio of m-/p-xylene-toethylbenzene demonstrated that there were more prominent atmospheric photochemical reactions in summer than that in winter.Finally,according to the potential source contribution function(PSCF)results,compared with local pollution sources,the spread of pollution from long-distance VOCs had a greater impact on Beijing.

Rotational motions of the Ms7.0 Jiuzhaigou earthquake with ground tilt data

Observation and research of rotational motions induced by earthquake has been ignored in the past decades due to the lack of understanding of important ground rotational motions and practical difficulty involved in directly measuring the rotational components. Currently, there is a paucity of methods to directly measure rotational motions in China. The present study attempts to discuss the possibility of obtaining seismic rotation from ground tilt data. The rotational motions generated by shear dislocation source are derived based on the displacement formula of elastic wavefields in the homogenous space. The characteristics of the three components of translational and rotational motions in near, intermediate, and far fields are compared and analyzed. Based on the corresponding relationship between the rotation and ground tilt on free surface boundary, a method to indirectly construct the rotational motions in the layered half space is obtained. Finally, the theoretical rotational motions generated by the Ms7.0 earthquake in Jiuzhaigou, Sichuan Province, on August 8, 2017 are calculated. The results indicate that the rotational motions generated by the Jiuzhaigou earthquake are concentrated in the vicinity of the epicenter(approximately150 km) and mainly distributed in the area perpendicular to the fault strike. The existence of free surface boundary attenuates the total energy of the rotational field and especially in the direction of the dominant energy. The ground tilt data is compared with rotational motions in the layered half space, and the results indicate that theoretical rotations and actual ground tilt data are essentially consistent, especially in the far field region. Thus, it is possible to obtain horizontal components of rotation from ground tilt data, and this provides more information for a complete description of the motion characteristics of an underground medium.

Microstructure and Tribological Properties of Plasma Nitriding Cast CoCrMo Alloy

A medical cast CoCrMo alloy was coated by plasma nitriding process to enhance the wear resistance.The microstructures,phases and micro-hardness of nitrided layers were investigated by atomic force microscopy(AFM),scanning electron microscopy(SEM),X-ray diffraction(XRD) and micro-hardness.Tribological properties were investigated on a pin-on-disc wear tester under 25% bovine serum solutions.The experimental results showed that plasma nitriding was a promising process to produce thick,hard and wear resistant layers on the surface of CoCrMo alloy.The harder CrN and Cr2N phases formed on the plasma nitrided layer with the compact nano-crystalline structure.Compared with the untreated sample,all nitrided samples showed the lower wear rates and higher wear resistance at different applied loads and nitriding temperatures.It was concluded that the improvement of wear resistance could be ascribed to the formation of thicker and harder nitrided layers with the specific microstructures on nitrided surfaces.

Incidence and prevalence of moyamoya disease in urban China: a nationwide retrospective cohort study

Background and objective Moyamoya disease(MMD)is an increasingly recognised cause of stroke,mainly described in East Asia.China is the largest nation in Asia,but few studies reported the epidemiology of MMD,especially at a national level.We aimed to estimate the incidence and prevalence of MMD in China.Methods We performed a population-based study using data from the national databases of Urban Basic Medical Insurance between 2013 and 2016,covering approximately 0.50 billion individuals.MMD cases were identified by diagnostic code(International Classification of Diseases,10th Revision I67.5)or related diagnostic text.Results A total of 1987 MMD patients(mean age 44.45±14.30 years,female-to male ratio 1.12)were identified,representing a national crude incidence of 0.59(95%CI:0.49 to 0.68)and a prevalence of 1.01(95%CI:0.81 to 1.21)per 100000 person-years in 2016.Rates were higher in females than in males for the incidence(0.66 vs 0.52)and prevalence(1.05 vs 0.90).And the age-specific rates showed a bimodal distribution,with the highest peak in middle-aged group and the second peak in child group.Conclusions Our results confirm that MMD is relatively common in East Asians,but the rates in China were lower than those in other East Asian countries such as Japan and Korea.The unique epidemiological features,including a relatively weak female predominance and a shift in the highest peak of incidence from children to adults,revealed new sight into MMD.Further research is expected to explore the potential pathogenesis of MMD.

Interseismic and coseismic displacements of the Lushan Ms 7.0 earthquake inferred from leveling measurements

By using precise leveling data observed between 1985 and 2010 across the south section of the Longmenshan fault zone,and eliminating the coseismic displacements caused by the Wenchuan Ms 8.0 earthquake,the interseismic vertical deformation field was obtained.The result shows that the Lushan region,located between the Shuangshi–Dachuan fault(front range of the Longmenshan fault) and the Xinkaidian fault(south section of the Dayi fault),is situated in the intersection zone of positive and negative vertical deformation gradient zones,indicating that this zone was locked within 25 years before the Lushan earthquake.Based on leveling data across the rupture zone surveyed between 2010 and 2013,and by eliminating the vertical deformation within 3 years before the earthquake,the coseismic vertical displacement was derived.The coseismic vertical displacement for the benchmark DD35,which is closest to the epicenter,is up to198.4 mm(with respect to MY165A).The coseismic displacement field revealed that the northwest region(hanging wall) moved upwards in comparison with the southeastern region(foot wall),suggesting that the seismogenic fault mainly underwent thrust faulting.By comparing the coseismic and interseismic vertical deformation fields,it was found that the mechanisms of this earthquake are consistent with the elastic rebound theory; the elastic strain energy(displacement deficit) accumulated before the Lushan earthquake was released during this quake.

Structure,tribological properties,and the growth mechanism of in-situ generated TiC in titanium cermet

Titanium cermet combining metallic toughness with ceramic wear resistance has been proven to be a potential candidate for implanted joint material.In this work,titanium cermet was synthesized by means of the elevated temperature solid carburizing technology.The Ti_(13)Nb_(13)Zr alloy surface was found to be converted into TiC ceramic layer combined with a carbon strengthened diffusion zone underneath.The overall thickness of the carburized region grew to about 100 um after 120 min carburization at 1,500 K.In order to clarify the growth behaviors of TiC ceramic layer,a growth mechanism is proposed.At the beginning of carburizing process,carbonaceous gas decomposed from carburizer due to high temperature and then converted to free atomic carbons through reduction reaction.Then,in-situ generated TiC ceramic layer possessing certain thickness formed on the surface,meanwhile,the inner carbon diffusion zone also grew inwards due to physical diffusion of carbon,and finally forming a gradient carbon distribution.In addition,the tribological behaviors of the new materials were evaluated through reciprocating ball-on-plate sliding wear tests in bovine calf serum.Although there was an increase in friction coefficient,the wear rate decreased by 59.6%due to the formation of the wear-resistant TiC ceramic layer.The wear mechanisms evolved from severe abrasive wear for bare Ti_(13)Nb_(13)Zr alloy to mild adhesive wear for titanium cermet.

Kilometer-resolution three-dimensional crustal deformation of Tibetan Plateau from InSAR and GNSS

Located at the forefront of the collision between the Indian and Eurasian Plates,the Tibetan Plateau experiences intense crustal movement.Traditional ground-based geodetic monitoring,such as GNSS and leveling,is challenging,due to factors such as high altitude and harsh climate,making it difficult to accurately determine a high-resolution crustal deformation field of the plateau.Unaffected by ground observation conditions,InSAR technique has key advantages for obtaining extensive and high-resolution crustal deformation fields.This makes it indispensable for crustal deformation monitoring on the Tibetan Plateau.This study used Sentinel-1 data from 2014 to 2020 to compute the ascending and descending InSAR deformation fields for the Tibetan Plateau.This was conducted with a measurement accuracy of approximately 3 mm/yr.Building upon this,we integrated InSAR and GNSS data to yield kilometer-resolution three-dimensional(3D)crustal deformation and strain rate fields for the Tibetan Plateau.A spherical wavelet analysis was used to decompose the 3D deformation field and separate the nontectonic crustal deformation to increase the strength of the tectonic deformation signal.Short-wavelength(<110 km)deformations match the distribution of fault movement,post-seismic deformations,and other non-tectonic factors.Long wavelength(>110 km)deformation mainly results from subsidence in the central plateau and uplifts along the Himalayan Arc.This indicates that the Tibetan Plateau may have stopped the entire uplift and entered a local collapse stage.Furthermore,the deformation fields at different spatial scales reveal that the plateau exhibits discontinuous deformation in short wavelengths and continuous deformation in long wavelengths.The findings of this study contribute to resolving the controversy between the Block and Continuum Deformation models of the Tibetan Plateau.