Based on the waveform data of 5,076 local earthquakes recorded at 25 stations in Xinjiang during the period from 2009 to 2014 and the observation reports provided by the Xinjiang Digital Seismic Network,a data set of ...Based on the waveform data of 5,076 local earthquakes recorded at 25 stations in Xinjiang during the period from 2009 to 2014 and the observation reports provided by the Xinjiang Digital Seismic Network,a data set of 19,140 attenuation factors t*is obtained by fitting the high-frequency attenuation of S-wave spectra with a genetic algorithm. The spatial distribution of Q_S is determined by inverting the t*data with seismic tomography. The results show that the average Q0 in eastern Tianshan is 520,and there is a significant correlation between the Q_S value distribution or attenuation characteristics it disclosed and the surface structure of the study area. The Q_S value is lower in the intersection area of the mountain basin which is located on the north and south sides of the Tianshan Mountains,and the high Q_S distribution is more concentrated inside the Tianshan orogenic belt. The M≥6. 0 earthquakes have been basically located in the Low-Q_S region since 1900. 24 high heat flow points in eastern Tianshan are located at the north and south of Tianshan Mountains where low Q_S exists,indicating a negative correlation. In addition,there is a positive correlation between the velocity structure and the attenuation structure in the study area,which reflects the consistency of the 2-D attenuation structure with the velocity structure and the two-dimensional density structure.展开更多
Hypoxia（low oxygen level） is an important feature during infections and affects the host defence mechanisms. The host has evolved specific responses to address hypoxia, which are strongly dependent on the activation...Hypoxia（low oxygen level） is an important feature during infections and affects the host defence mechanisms. The host has evolved specific responses to address hypoxia, which are strongly dependent on the activation of hypoxia-inducible factor 1（HIF-1）.Hypoxia interferes degradation of HIF-1 alpha subunit（HIF-1α）, leading to stabilisation of HIF-1α, heterodimerization with HIF-1 beta subunit（HIF-1β） and subsequent activation of HIF-1 pathway. Apical periodontitis（periapical lesion） is a consequence of endodontic infection and ultimately results in destruction of tooth-supporting tissue, including alveolar bone. Thus far, the role of HIF-1 in periapical lesions has not been systematically examined. In the present study, we determined the role of HIF-1 in a wellcharacterised mouse periapical lesion model using two HIF-1α-activating strategies, dimethyloxalylglycine（DMOG） and adenovirusinduced constitutively active HIF-1α（CA-HIF1 A）. Both DMOG and CA-HIF1 A attenuated periapical inflammation and tissue destruction. The attenuation in vivo was associated with downregulation of nuclear factor-κappa B（NF-κB） and osteoclastic gene expressions. These two agents also suppressed NF-κB activation and subsequent production of proinflammatory cytokines by macrophages. Furthermore, activation of HIF-1α by DMOG specifically suppressed lipopolysaccharide-stimulated macrophage differentiation into M1 cells, increasing the ratio of M2 macrophages against M1 cells. Taken together, our data indicated that activation of HIF-1 plays a protective role in the development of apical periodontitis via downregulation of NF-κB, proinflammatory cytokines, M1 macrophages and osteoclastogenesis.展开更多
Comprehensive experimental and numerical studies have been undertaken to investigate wave energy dissipation performance and main influencing factors of a lower arc-plate breakwater. The numerical model, which conside...Comprehensive experimental and numerical studies have been undertaken to investigate wave energy dissipation performance and main influencing factors of a lower arc-plate breakwater. The numerical model, which considers nonlinear interactions between waves and the arc-plate breakwater, has been constructed by using the velocity wave- generating method, the volume of fluid (VOF) method and the finite volume method. The results show that the relative width, relative height and relative submergence of the breakwater are three main influencing factors and have significant influence on wave energy dissipation of the lower arc-plate open breakwater. The transmission coefficient is found to decrease with the increasing relative width, and the minimum transmission coefficient is 0.15 when the relative width is 0.45. The reflection coefficient is found to vary slightly with the relative width, and the maximum reflection coefficient is 0.53 when the relative width is 0.45. The transmission and reflection coefficients are shown to increase with the relative wave height for approximately 85% of the experimental tests when the relative width is 0.19 0.45. The transmission coefficients at relative submergences of 0.04, 0.02 and 0 are clearly shown to be greater than those at relative submergences of 0.02 and 0.04, while the reflection coefficient exhibits the opposite relationship. After the wave interacts with the lower arc-plate breakwater, the wave energy is mainly converted into transmission, reflection and dissipation energies. The wave attenuation performance is clearly weakened for waves with greater heights and longer periods.展开更多
Low-rise buildings are susceptible to high-frequency ground motion.The high-frequency ground motions at regional distances are mainly controlled by crustal Lg waves whose amplitudes are typically much larger than thos...Low-rise buildings are susceptible to high-frequency ground motion.The high-frequency ground motions at regional distances are mainly controlled by crustal Lg waves whose amplitudes are typically much larger than those of body waves.In this study,we develop a Lg-wave Q model for the Sichuan and Yunnan region in the frequency band of 0.3–2.0 Hz using regional seismic records of 1166 earthquakes recorded at 152 stations.Comparison between the observed pattern of ground motion from real earthquake and model prediction demonstrates the robustness and effectiveness of our Lg-Q model.Then,assuming that the Lg-wave Q structure is the main factor affecting the propagation of the high-frequency ground motions,we calculate the spatial distributions of high-frequency ground motions from scenario earthquakes at different locations in the region using the average Lg-wave attenuation model over the frequency band of 0.3–2.0 Hz.We also use the Lg-Q model to estimate the distribution of cumulative energy of high-frequency ground motions based on the historical seismicity of the Sichuan and Yunnan region.Results show that the Lg-Q model can be used effectively in estimating the spatial distribution of high-frequency seismic energies and thus can contribute to the assessment of seismic hazard to low-rise buildings.展开更多
Based on the Gauss linear frequency modulated wavelet transform, a new characteristic index is presented, namely time frequency energy attenuation factor which can reflect the difference features of waveform in earthq...Based on the Gauss linear frequency modulated wavelet transform, a new characteristic index is presented, namely time frequency energy attenuation factor which can reflect the difference features of waveform in earthquake focus mechanism, wave traveling path and its attenuation characteristics in focal area or near field. In order to test its validity, we select the natural earthquakes and explosion or collapse events whose focus mechanisms vary obviously,and some natural earthquakes located at the same site or in a very small area. The study indicates that the time frequency energy attenuation factors of the natural earthquakes are obviously different with that of explosion or collapse events, and the change of the time frequency energy attenuation factors is relatively stable for the earthquakes under the normal seismicity background. Using the above mentioned method, it is expected to offer a useful criterion for strong earthquake prediction by continuous earthquake observation.展开更多
To assess the groundwater vulnerability due to leaching of chemicals, the groundwater system in the unsaturated zone is characterized by conceptual models that are further extended and refined with more detailed mathe...To assess the groundwater vulnerability due to leaching of chemicals, the groundwater system in the unsaturated zone is characterized by conceptual models that are further extended and refined with more detailed mathematical models to understand the governing physical processes in detail. However, due to lack of data and uncertainty level, an intermediate transition through index based models is researched. The attenuation factor (AF) approach, which works under the assumption that the chemicals degrade following a first-order kinetics and determines the fraction of the chemicals that goes to groundwater table, is one of the index based models that has been widely used due to its simplicity. Therefore, the objective of this paper is to review the research works done using the AF approach, to outline the future research needs. Furthermore, the mathematical implementation of the AF approach and the associated uncertainty levels is explained through an example and MATLAB source code.展开更多
The analysis of fractured reservoirs is very important to hydrocarbon exploration. The quality factor Q is a parameter used to characterize the attenuation of seismic waves in subsurface media. Q not only reflects the...The analysis of fractured reservoirs is very important to hydrocarbon exploration. The quality factor Q is a parameter used to characterize the attenuation of seismic waves in subsurface media. Q not only reflects the inherent properties of the medium but also is used to make predictions regarding reservoir fractures. Compared with poststack seismic data, prestack seismic data contain detailed stratigraphic information of seismic attributes and data inversion in reservoirs. The extraction of absorption parameters from prestack data improves the accuracy of attenuation estimates. In this study, I present a new method for calculating Q based on the modified S transform （MST） using common midpoint （CMP） preprocessed gathers. First, I use the MST with adjustable time-frequency resolution to carry out a high-precision time-frequency analysis of prestack CMP gathers and derive the calculation formula for the improved S transform-based frequency spectrum ratio method. Then, I use the energy density ratio to calculate the slope of the frequency spectrum ratio instead of the conventional amplitude ratio. Thus, I establish the relation between the slope of the spectrum ratio and offset as well as eliminate the offset effect by multichannel linear fitting, obtaining accurate Q values from seismic prestack data. Finally, I use the proposed prestack Q extraction method to study the fractured reservoir in Qianjin burried hill and P-wave absorption and attenuation anisotropy with good results in the fracture characterization.展开更多
To facilitate investigation of the effect of imperfect elastic dissipation on the propagation of Rayleigh-type channel waves and use of their quality factors in investigations of the properties of coal seams, a simple...To facilitate investigation of the effect of imperfect elastic dissipation on the propagation of Rayleigh-type channel waves and use of their quality factors in investigations of the properties of coal seams, a simple method for calculating the quality factor QR is proposed in this paper. Introduction of complex velocities into the dispersion function allows calculation of the dispersion function of Rayleigh-type channel waves in coal seams. By the control variable method, we analyzed changes in QR with changes in coal seam thickness and P- and S-wave Q-factors within the coal seam and adjacent rock layers. The numerical results show that the trend of the QR curve is consistent with the group velocity curve. The minimum QR value occurs at the Airy phase frequency; the Airy phase frequency decreases as coal seam thickness increases. The value of QR increases with increasing QS2(quality factor for S wave in coal seam). We can compensate for the absorption of Rayleigh-type channel waves using the computed QR curve. Inversion of the QR curve can also be used to predict the thicknesses and lithologies of coal seams.展开更多
AIM:To investigate the effect of keratinocyte growth factor(KGF) gene therapy in acetic acid-induced ulcerative colitis in rat model.METHODS:The colitis of Sprague-Dawley rats was induced by intrarectal infusion of 1 ...AIM:To investigate the effect of keratinocyte growth factor(KGF) gene therapy in acetic acid-induced ulcerative colitis in rat model.METHODS:The colitis of Sprague-Dawley rats was induced by intrarectal infusion of 1 mL 5%(v/v) acetic acid.Twenty-four hours after exposed to acetic acid,rats were divided into three experimental groups:control group,attenuated Salmonella typhimurium Ty21a strain(SP) group and SP strain carrying human KGF gene(SPK) group,and they were separately administered orally with 10% NaHCO3,SP or SPK.Animals were sacrificed and colonic tissues were harvested respectively on day 3,5,7 and 10 after administration.Weights of rats,colonic weight/length ratio and stool score were evaluated.Histological changes of colonic tissues were examined by hematoxylin and eosin(HE) staining method.The expression of KGF,KGF receptor(KGFR) and TNF-α were measured either by enzyme-linked immunosorbent assay or Western blotting.Immunohistochemistry was used to detect the cellular localization of KGFR and Ki67.In addition,superoxide dismutase(SOD) activity and malondialdehyde(MDA) contents in the homogenate were measured.RESULTS:Body weight and colonic weight/length ratio were declined in SPK group compared with SP and control groups(body weight:272.78 ± 17.92 g vs 243.72 ± 14.02 g and 240.68 ± 12.63 g,P < 0.01;colonic weight/length ratio:115.76 ± 7.47 vs 150.32 ± 5.99 and 153.67 ± 5.50 mg/cm,P < 0.01).Moreover,pathological changes of damaged colon were improved in SPK group as well.After administration of SPK strain,KGF expression increased markedly from the 3rd d,and remained at a high level till the 10th d.Furthermore,KGFR expression and Ki67 expression elevated,whereas TNF-α expression was inhibited in SPK group.In the group administered with SPK,SOD activity increased significantly(d 5:26.18 ± 5.84 vs 18.12 ± 3.30 and 18.79 ± 4.74 U/mg,P < 0.01;d 7:35.48 ± 3.35 vs 22.57 ± 3.44 and 21.69 ± 3.94 U/mg,P < 0.01;d 10:46.10 ± 6.23 vs 25.35 ± 4.76 and 27.82 ± 6.42 U/mg,P < 0.01) and MDA contents decreased accordingly(d 7:7.40 ± 0.88 vs 9.81 ± 1.21 and 10.45 ± 1.40 nmol/mg,P < 0.01;d 10:4.36 ± 0.62 vs 8.41 ± 0.92 and 8.71 ± 1.27 nmol/mg,P < 0.01),compared with SP and control groups.CONCLUSION:KGF gene therapy mediated by attenuated Salmonella ameliorates ulcerative colitis induced by acetic acids,and it may be a safe and effective treatment for ulcerative colitis.展开更多
On the condition that the velocity ratio of compressive wave to shear wave is stable during the propagating process of seismic wave, this paper develops an estimation method for medium quality factor based on single s...On the condition that the velocity ratio of compressive wave to shear wave is stable during the propagating process of seismic wave, this paper develops an estimation method for medium quality factor based on single station＇s travel time difference between direct S and P waves and the first period signal of direct P wave. 8 774 high SNR wave data altogether recorded by 75 stations are analyzed. The results show that： （1） under the normal regional stress field, the quality factors QmsP in the stable tectonic area are higher than that in the active tectonic area around the Weifang-Jiashan section and its surrounding area in the Tanlu fault zone; （2） in the Juxian-Tancheng section the seismic wave attenuation is relatively quick, and the media is relatively broken, suggesting no tectonic stress accumulation; （3） the Xinyi-Sihong section is currently locking and in accumulating elastic strain energy stage, which has the deep environment and conditions of strong earthquake generation similar to those of the 1668 M8.5 Tancheng strong earthquake.展开更多
The quality factor(or Q value)is an important parameter for characterizing the inelastic properties of rock.Achieving a Q value estimation with high accuracy and stability is still challenging.In this study,a new meth...The quality factor(or Q value)is an important parameter for characterizing the inelastic properties of rock.Achieving a Q value estimation with high accuracy and stability is still challenging.In this study,a new method for estimating ultrasonic attenuation using a spectral ratio based on an S transform(SR-ST)is presented to improve the stability and accuracy of Q estimation.The variable window of ST is used to solve the time window problem.We add two window factors to the Gaussian window function in the ST.The window factors can adjust the scale of the Gaussian window function to the ultrasonic signal,which reduces the calculation error attributed to the conventional Gaussian window function.Meanwhile,the frequency bandwidth selection rules for the linear regression of the amplitude ratio are given to further improve stability and accuracy.First,the feasibility and influencing factors of the SR-ST method are studied through numerical testing and standard sample experiments.Second,artificial samples with different Q values are used to study the adaptability and stability of the SR-ST method.Finally,a further comparison between the new method and the conventional spectral ratio method(SR)is conducted using rock field samples,again addressing stability and accuracy.The experimental results show that this method will yield an error of approximately 36%using the conventional Gaussian window function.This problem can be solved by adding the time window factors to the Gaussian window function.The frequency bandwidth selection rules and mean slope value of the amplitude ratio used in the SR-ST method can ensure that the maximum error of different Q values estimation(Q>15)is less than 10%.展开更多
Based on 266 strong ground motion records, an attenuation relationship was developed for both absolute and relative input energy spectra. The comparison of the two kinds of input energy spectra constructed from the at...Based on 266 strong ground motion records, an attenuation relationship was developed for both absolute and relative input energy spectra. The comparison of the two kinds of input energy spectra constructed from the attenuation relationship was made in this paper. The results show that there is little difference between the absolute input energy spectra and relative input energy spectra at the periods of 0.5-1.0 s for elastic systems and at the period of 0.5 s for inelastic systems. The absolute input energy spectra are much larger than relative input energy spectra in very short period range but some less than relative input energy spectra in long period range. It is also found that the ductility factor has a significant effect on both absolute and relative input energy spectra. The absolute input energy spectra increase with the increasing of ductility factor in the period range of less than 0.3 s but decrease in the period range of larger than 0.3 s. The absolute input energy spectra for different ductility factor are almost equivalent at the period about 0.3 s, but for relative input energy spectra, the period is about 0.5 s. The effect of ductility on the relative input energy spectra in the short period range is much larger than that on the absolute input energy spectra, especially on the softer site class.展开更多
We investigate attenuation scattering and loss properties in Souss basin(SW of High-Atlas) as a transition zone between the High and Anti Atlas ranges. This district consists in a thinned crustal patch with shallow se...We investigate attenuation scattering and loss properties in Souss basin(SW of High-Atlas) as a transition zone between the High and Anti Atlas ranges. This district consists in a thinned crustal patch with shallow seismicity and loose sedimentary trenches that perform an important contribution to augment seismic attenuation. So far, no coda waves approach in our knowledge have been used to draw satisfying outputs about the attenuation properties in the region. Therefore, this update suggests to correlate the lateral changes of seismic attenuation to different characteristics and asperities i.e. seismic activity,crustal age and thickness, heat flow, and ground deformation rate. To do so, we analysed coda waves derived from waveform data of more than 23 local earthquakes from seven broadband seismometers recorded during 2010 e2012 period. As a starter, we utilized the backscattering model which defines theseismic attenuation as inversely proportional to quality factor by the equation A ?1=. QQcestimates c were deducted at various central frequency bands 1.5, 3.0, 6.0, 9.0, 12.0 and 18.0 Hz according to different lapses times. The estimated average frequency dependence quality factor gives relation Qc? 120 f1;01,while the average Qcvalues vary from 149 at 1.5 Hz to 1895 at 18 Hz central frequencies. We observed an intimate dependence between quality factor and frequency ranges, which reflects the complexity of geological/geophysical pattern in the Souss basin and the presence of a variety of heterogeneities within the underlying crust.展开更多
In this paper, according to the relationship of observation spectrum with source spectrum, travel-path attenuation factor and site effect, we use the digital seismic data of moderate-small earthquakes to invert the so...In this paper, according to the relationship of observation spectrum with source spectrum, travel-path attenuation factor and site effect, we use the digital seismic data of moderate-small earthquakes to invert the soft rock site effect and S wave inelastic attenuation under the constraint of site effect, and determine the parameters of path and site. The parameters obtained by this method exclude the topographic effect of seismic stations, and truly reflect the seismic effect of free soft rock sites and the S wave inelastic attenuation in the studied region. The average soft rock site effect is about 1.5 times in the frequency domain of 2-4 Hz and the S wave quality factor is obtained as Qs=278f0.346, which can be directly applied to the stochastic modeling of ground motions in the studied region.展开更多
An inversion method was applied to crustal earthquakes dataset to find S-wave attenuation characteristics beneath the Eastern Tohoku region of Japan. Accelerograms from 85 shallow crustal earthquakes up to 25 km depth...An inversion method was applied to crustal earthquakes dataset to find S-wave attenuation characteristics beneath the Eastern Tohoku region of Japan. Accelerograms from 85 shallow crustal earthquakes up to 25 km depth and magnitude range between 3.5 and 5.5 were analyzed to estimate the seismic quality factor Qs. A homogeneous attenuation model Qs for the wave propagation path was evaluated from spectral amplitudes, at 24 different frequencies between 0.5 and 20 Hz by using generalized inversion technique. To do this, non-parametric attenuation functions were calculated to observe spectral amplitude decay with hypocentral distance. Then, these functions were parameterized to estimate Qs. It was found that in Eastern Tohoku region, the Qs frequency dependence can be approximated with the function 33 f 1.22 within a frequency range between 0.5 and 20 Hz. However, the frequency dependence of Qs in the frequency range between 0.5 and 6 Hz is best approximated by Qs （f） = 36 f 0.94 showing relatively weaker frequency dependence as compared to the relation Qs （f） = 6 f^ 2.09 for the frequency range between 6 and 15 Hz. These results could be used to estimate source and site parameters for seismic hazard assessment in the region.展开更多
The frequency-dependent characteristics of P- and S-wave attenuation in the upper crust of NW Himalayas have been estimated using local earthquakes for a frequency range of 1.5 to 18 Hz. A total of 43 local events of ...The frequency-dependent characteristics of P- and S-wave attenuation in the upper crust of NW Himalayas have been estimated using local earthquakes for a frequency range of 1.5 to 18 Hz. A total of 43 local events of magnitude 2.1 - 4.8, mostly from the vicinity of Main Boundary Thrust (MBT) and Main Central Thrust (MCT) have been used in the analysis. The extended coda normalization methods were applied to estimate the quality factors for P- waves (QP) and S-waves (QS) and the single back-scattering model has been used earlier (Kumar et al. [1]) to determine the quality factor for coda waves (QC). The observed quality factors QP and QS is strongly frequency dependent and the estimated average frequency dependent relation is given by QP = (97 ± 3)f (1.06 ± 0.06) and QS = (127 ± 6)f (0.96±0.06) respectively for P- and S-waves. A comparison of QS estimated in this study and QC previously reported shows that QC > QS for entire frequency range. This indicates the enrichment of coda waves and the importance of scattering attenuation to the attenuation of S-waves in the study region infested with faults and fractures. The ratio QS/QP is found to be greater than unity for the entire frequency range indicating that the body waves from source to station paths crossed a crustal volume with dry and rigid rocks. The frequency dependent relations developed in this study can be very useful to ground motion modeling which in turn is required in the seismic hazard assessment of the region.展开更多
Dispersion and attenuation analysis can be used to determine formation anisotropy induced by fractures,or stresses.In this paper,we propose a nonparametric spectrum estimation method to get phase dispersion characteri...Dispersion and attenuation analysis can be used to determine formation anisotropy induced by fractures,or stresses.In this paper,we propose a nonparametric spectrum estimation method to get phase dispersion characteristics and attenuation coefficient.By designing an appropriate vector filter,phase velocity,attenuation coefficient and amplitude can be inverted from the waveform recorded by the receiver array.Performance analysis of this algorithm is compared with Extended Prony Method(EPM)and Forward and Backward Matrix Pencil(FBMP)method.Based on the analysis results,the proposed method is capable of achieving high resolution and precision as the parametric spectrum estimation methods.At the meantime,it also keeps high stability as the other nonparametric spectrum estimation methods.At last,applications to synthetic waveforms modeled using finite difference method and real data show its efficiency.The real data processing results show that the P-wave attenuation log is more sensitive to oil formation compared to S-wave;and the S-wave attenuation log is more sensitive to shale formation compared to P-wave.展开更多
Accurately estimated interval attenuation(1/Q)values have several applications,such as in quantitative interpretation and seismic resolution enhancement.Although Q values can be estimated by measuring the spectral rat...Accurately estimated interval attenuation(1/Q)values have several applications,such as in quantitative interpretation and seismic resolution enhancement.Although Q values can be estimated by measuring the spectral ratio between seismic reflections from a target and a reference reflector,the results are influenced by factors such as overburden inhomogeneities.Here,we quantitatively analyze the overburden influence on interval Q estimations using the spectral ratio method,time-space domain prestack Q inversion(PSQI),andτ-p domain PSQI.We compare these three methods using a synthetic dataset and a field dataset acquired onshore the Arabian Peninsula.Synthetic seismic gathers are generated from a three-layer model with a low-Q inclusion in the first layer to mimic overburden inhomogeneity.The fi eld data are preconditioned image gathers from a producing oil fi eld.The synthetic data test shows that the small low-Q body produces a considerable error in estimated Q values.The smallest error(i.e.,13.3%)is in theτ-p domain PSQI result.Theoretically,τ-p domain PSQI could obtain more accurate Q values when there are overburden infl uences because of the simultaneous inversion scheme and the application in theτ-p domain.The fi eld data application also illustrates that theτ-p domain PSQI produces reasonable interval Q values.Our measured Q values are also comparable with the Q values estimated from hydrocarbon saturated carbonate reservoirs.展开更多
To answer the queries concerning penetrability of ~1 μT, physiologically patterned, time-varying magnetic fields through the cranium, the proportions of attenuation through thicknesses and densities of ~3 times that ...To answer the queries concerning penetrability of ~1 μT, physiologically patterned, time-varying magnetic fields through the cranium, the proportions of attenuation through thicknesses and densities of ~3 times that of the human skull were measured directly. There was no reduction in the intensity of the magnetic field when two 2 cm thick dried pine boards (4.3 × 103 kg·m-3) were placed between the pairs of solenoids separated by the approximate width of the skull. Although volumes of water containing intracellular concentrations of ions did not attenuate the field intensity, placement of 290 cm2 of 2 mm sheets of duct metal reduced the amplitude by 25%. Spectra comparisons showed a clear congruence in profiles between direct measurement of the applied field and the original computer-generated pattern. These results indicate there is little validity to claims that weak, time-varying magnetic fields applied in this manner are eliminated or significantly attenuated by the human skull.展开更多
基金jointly funded by the Contract Oriented Work Task for Seismic Situation in 2017(2017010104)Science for Earthquake Resilience(XH17041Y)Fund of Earthquake Agency of Xinjiang Uygur Autonomous Region(201401)
文摘Based on the waveform data of 5,076 local earthquakes recorded at 25 stations in Xinjiang during the period from 2009 to 2014 and the observation reports provided by the Xinjiang Digital Seismic Network,a data set of 19,140 attenuation factors t*is obtained by fitting the high-frequency attenuation of S-wave spectra with a genetic algorithm. The spatial distribution of Q_S is determined by inverting the t*data with seismic tomography. The results show that the average Q0 in eastern Tianshan is 520,and there is a significant correlation between the Q_S value distribution or attenuation characteristics it disclosed and the surface structure of the study area. The Q_S value is lower in the intersection area of the mountain basin which is located on the north and south sides of the Tianshan Mountains,and the high Q_S distribution is more concentrated inside the Tianshan orogenic belt. The M≥6. 0 earthquakes have been basically located in the Low-Q_S region since 1900. 24 high heat flow points in eastern Tianshan are located at the north and south of Tianshan Mountains where low Q_S exists,indicating a negative correlation. In addition,there is a positive correlation between the velocity structure and the attenuation structure in the study area,which reflects the consistency of the 2-D attenuation structure with the velocity structure and the two-dimensional density structure.
基金supported by the National Institute of Dental and Craniofacial Research(NIDCR)the National Center for Research Resources(NCRR)of the National Institutes of Health(NIH)under award numbers R21DE023178,R01DE024796,and S10RR027553
文摘Hypoxia（low oxygen level） is an important feature during infections and affects the host defence mechanisms. The host has evolved specific responses to address hypoxia, which are strongly dependent on the activation of hypoxia-inducible factor 1（HIF-1）.Hypoxia interferes degradation of HIF-1 alpha subunit（HIF-1α）, leading to stabilisation of HIF-1α, heterodimerization with HIF-1 beta subunit（HIF-1β） and subsequent activation of HIF-1 pathway. Apical periodontitis（periapical lesion） is a consequence of endodontic infection and ultimately results in destruction of tooth-supporting tissue, including alveolar bone. Thus far, the role of HIF-1 in periapical lesions has not been systematically examined. In the present study, we determined the role of HIF-1 in a wellcharacterised mouse periapical lesion model using two HIF-1α-activating strategies, dimethyloxalylglycine（DMOG） and adenovirusinduced constitutively active HIF-1α（CA-HIF1 A）. Both DMOG and CA-HIF1 A attenuated periapical inflammation and tissue destruction. The attenuation in vivo was associated with downregulation of nuclear factor-κappa B（NF-κB） and osteoclastic gene expressions. These two agents also suppressed NF-κB activation and subsequent production of proinflammatory cytokines by macrophages. Furthermore, activation of HIF-1α by DMOG specifically suppressed lipopolysaccharide-stimulated macrophage differentiation into M1 cells, increasing the ratio of M2 macrophages against M1 cells. Taken together, our data indicated that activation of HIF-1 plays a protective role in the development of apical periodontitis via downregulation of NF-κB, proinflammatory cytokines, M1 macrophages and osteoclastogenesis.
基金supported by the NSFC-Shandong Joint Fund(Grant Nos.U1706220 and U1806227)the National Natural Science Foundation of China(Grant Nos.51709140 and 51879019)the Key Laboratory of Coastal Disasters and Defence of Ministry of Education(Grant No.201703)
文摘Comprehensive experimental and numerical studies have been undertaken to investigate wave energy dissipation performance and main influencing factors of a lower arc-plate breakwater. The numerical model, which considers nonlinear interactions between waves and the arc-plate breakwater, has been constructed by using the velocity wave- generating method, the volume of fluid (VOF) method and the finite volume method. The results show that the relative width, relative height and relative submergence of the breakwater are three main influencing factors and have significant influence on wave energy dissipation of the lower arc-plate open breakwater. The transmission coefficient is found to decrease with the increasing relative width, and the minimum transmission coefficient is 0.15 when the relative width is 0.45. The reflection coefficient is found to vary slightly with the relative width, and the maximum reflection coefficient is 0.53 when the relative width is 0.45. The transmission and reflection coefficients are shown to increase with the relative wave height for approximately 85% of the experimental tests when the relative width is 0.19 0.45. The transmission coefficients at relative submergences of 0.04, 0.02 and 0 are clearly shown to be greater than those at relative submergences of 0.02 and 0.04, while the reflection coefficient exhibits the opposite relationship. After the wave interacts with the lower arc-plate breakwater, the wave energy is mainly converted into transmission, reflection and dissipation energies. The wave attenuation performance is clearly weakened for waves with greater heights and longer periods.
基金supported by the China Postdoctoral Science Foundation
文摘Low-rise buildings are susceptible to high-frequency ground motion.The high-frequency ground motions at regional distances are mainly controlled by crustal Lg waves whose amplitudes are typically much larger than those of body waves.In this study,we develop a Lg-wave Q model for the Sichuan and Yunnan region in the frequency band of 0.3–2.0 Hz using regional seismic records of 1166 earthquakes recorded at 152 stations.Comparison between the observed pattern of ground motion from real earthquake and model prediction demonstrates the robustness and effectiveness of our Lg-Q model.Then,assuming that the Lg-wave Q structure is the main factor affecting the propagation of the high-frequency ground motions,we calculate the spatial distributions of high-frequency ground motions from scenario earthquakes at different locations in the region using the average Lg-wave attenuation model over the frequency band of 0.3–2.0 Hz.We also use the Lg-Q model to estimate the distribution of cumulative energy of high-frequency ground motions based on the historical seismicity of the Sichuan and Yunnan region.Results show that the Lg-Q model can be used effectively in estimating the spatial distribution of high-frequency seismic energies and thus can contribute to the assessment of seismic hazard to low-rise buildings.
文摘Based on the Gauss linear frequency modulated wavelet transform, a new characteristic index is presented, namely time frequency energy attenuation factor which can reflect the difference features of waveform in earthquake focus mechanism, wave traveling path and its attenuation characteristics in focal area or near field. In order to test its validity, we select the natural earthquakes and explosion or collapse events whose focus mechanisms vary obviously,and some natural earthquakes located at the same site or in a very small area. The study indicates that the time frequency energy attenuation factors of the natural earthquakes are obviously different with that of explosion or collapse events, and the change of the time frequency energy attenuation factors is relatively stable for the earthquakes under the normal seismicity background. Using the above mentioned method, it is expected to offer a useful criterion for strong earthquake prediction by continuous earthquake observation.
文摘To assess the groundwater vulnerability due to leaching of chemicals, the groundwater system in the unsaturated zone is characterized by conceptual models that are further extended and refined with more detailed mathematical models to understand the governing physical processes in detail. However, due to lack of data and uncertainty level, an intermediate transition through index based models is researched. The attenuation factor (AF) approach, which works under the assumption that the chemicals degrade following a first-order kinetics and determines the fraction of the chemicals that goes to groundwater table, is one of the index based models that has been widely used due to its simplicity. Therefore, the objective of this paper is to review the research works done using the AF approach, to outline the future research needs. Furthermore, the mathematical implementation of the AF approach and the associated uncertainty levels is explained through an example and MATLAB source code.
基金supported in part by National Science&Technology Major Project(Grant No.2011ZX05019-008)the National Basic Research Program of China(973 Program)(Granted No.2013CB228600)Science Foundation of China University of Petroleum,Beijing(Granted No.KYJJ2012-05-10)
文摘The analysis of fractured reservoirs is very important to hydrocarbon exploration. The quality factor Q is a parameter used to characterize the attenuation of seismic waves in subsurface media. Q not only reflects the inherent properties of the medium but also is used to make predictions regarding reservoir fractures. Compared with poststack seismic data, prestack seismic data contain detailed stratigraphic information of seismic attributes and data inversion in reservoirs. The extraction of absorption parameters from prestack data improves the accuracy of attenuation estimates. In this study, I present a new method for calculating Q based on the modified S transform （MST） using common midpoint （CMP） preprocessed gathers. First, I use the MST with adjustable time-frequency resolution to carry out a high-precision time-frequency analysis of prestack CMP gathers and derive the calculation formula for the improved S transform-based frequency spectrum ratio method. Then, I use the energy density ratio to calculate the slope of the frequency spectrum ratio instead of the conventional amplitude ratio. Thus, I establish the relation between the slope of the spectrum ratio and offset as well as eliminate the offset effect by multichannel linear fitting, obtaining accurate Q values from seismic prestack data. Finally, I use the proposed prestack Q extraction method to study the fractured reservoir in Qianjin burried hill and P-wave absorption and attenuation anisotropy with good results in the fracture characterization.
基金This work is supported by the National Natural Science Foundation of China （No. 41140033）.
文摘To facilitate investigation of the effect of imperfect elastic dissipation on the propagation of Rayleigh-type channel waves and use of their quality factors in investigations of the properties of coal seams, a simple method for calculating the quality factor QR is proposed in this paper. Introduction of complex velocities into the dispersion function allows calculation of the dispersion function of Rayleigh-type channel waves in coal seams. By the control variable method, we analyzed changes in QR with changes in coal seam thickness and P- and S-wave Q-factors within the coal seam and adjacent rock layers. The numerical results show that the trend of the QR curve is consistent with the group velocity curve. The minimum QR value occurs at the Airy phase frequency; the Airy phase frequency decreases as coal seam thickness increases. The value of QR increases with increasing QS2(quality factor for S wave in coal seam). We can compensate for the absorption of Rayleigh-type channel waves using the computed QR curve. Inversion of the QR curve can also be used to predict the thicknesses and lithologies of coal seams.
基金Supported by Postdoctoral Science Foundation of China,No.20060390192,200801243research grant from Science and Technology Department of Gansu Province,China,No.0708NKCA128
文摘AIM:To investigate the effect of keratinocyte growth factor(KGF) gene therapy in acetic acid-induced ulcerative colitis in rat model.METHODS:The colitis of Sprague-Dawley rats was induced by intrarectal infusion of 1 mL 5%(v/v) acetic acid.Twenty-four hours after exposed to acetic acid,rats were divided into three experimental groups:control group,attenuated Salmonella typhimurium Ty21a strain(SP) group and SP strain carrying human KGF gene(SPK) group,and they were separately administered orally with 10% NaHCO3,SP or SPK.Animals were sacrificed and colonic tissues were harvested respectively on day 3,5,7 and 10 after administration.Weights of rats,colonic weight/length ratio and stool score were evaluated.Histological changes of colonic tissues were examined by hematoxylin and eosin(HE) staining method.The expression of KGF,KGF receptor(KGFR) and TNF-α were measured either by enzyme-linked immunosorbent assay or Western blotting.Immunohistochemistry was used to detect the cellular localization of KGFR and Ki67.In addition,superoxide dismutase(SOD) activity and malondialdehyde(MDA) contents in the homogenate were measured.RESULTS:Body weight and colonic weight/length ratio were declined in SPK group compared with SP and control groups(body weight:272.78 ± 17.92 g vs 243.72 ± 14.02 g and 240.68 ± 12.63 g,P < 0.01;colonic weight/length ratio:115.76 ± 7.47 vs 150.32 ± 5.99 and 153.67 ± 5.50 mg/cm,P < 0.01).Moreover,pathological changes of damaged colon were improved in SPK group as well.After administration of SPK strain,KGF expression increased markedly from the 3rd d,and remained at a high level till the 10th d.Furthermore,KGFR expression and Ki67 expression elevated,whereas TNF-α expression was inhibited in SPK group.In the group administered with SPK,SOD activity increased significantly(d 5:26.18 ± 5.84 vs 18.12 ± 3.30 and 18.79 ± 4.74 U/mg,P < 0.01;d 7:35.48 ± 3.35 vs 22.57 ± 3.44 and 21.69 ± 3.94 U/mg,P < 0.01;d 10:46.10 ± 6.23 vs 25.35 ± 4.76 and 27.82 ± 6.42 U/mg,P < 0.01) and MDA contents decreased accordingly(d 7:7.40 ± 0.88 vs 9.81 ± 1.21 and 10.45 ± 1.40 nmol/mg,P < 0.01;d 10:4.36 ± 0.62 vs 8.41 ± 0.92 and 8.71 ± 1.27 nmol/mg,P < 0.01),compared with SP and control groups.CONCLUSION:KGF gene therapy mediated by attenuated Salmonella ameliorates ulcerative colitis induced by acetic acids,and it may be a safe and effective treatment for ulcerative colitis.
基金supported by National Natural Science Foundation of China(grant No.40974031)Shandong Provincial Natural Science Foundation(grant No.Y2007E09)Jiangsu Provincial Social Development Project(grant No.BE2009691)
文摘On the condition that the velocity ratio of compressive wave to shear wave is stable during the propagating process of seismic wave, this paper develops an estimation method for medium quality factor based on single station＇s travel time difference between direct S and P waves and the first period signal of direct P wave. 8 774 high SNR wave data altogether recorded by 75 stations are analyzed. The results show that： （1） under the normal regional stress field, the quality factors QmsP in the stable tectonic area are higher than that in the active tectonic area around the Weifang-Jiashan section and its surrounding area in the Tanlu fault zone; （2） in the Juxian-Tancheng section the seismic wave attenuation is relatively quick, and the media is relatively broken, suggesting no tectonic stress accumulation; （3） the Xinyi-Sihong section is currently locking and in accumulating elastic strain energy stage, which has the deep environment and conditions of strong earthquake generation similar to those of the 1668 M8.5 Tancheng strong earthquake.
基金supported by the Special Fund of the Institute of Geophysics,China Earthquake Administration(Nos.DQJB19B02 and DQJB17T04)
文摘The quality factor(or Q value)is an important parameter for characterizing the inelastic properties of rock.Achieving a Q value estimation with high accuracy and stability is still challenging.In this study,a new method for estimating ultrasonic attenuation using a spectral ratio based on an S transform(SR-ST)is presented to improve the stability and accuracy of Q estimation.The variable window of ST is used to solve the time window problem.We add two window factors to the Gaussian window function in the ST.The window factors can adjust the scale of the Gaussian window function to the ultrasonic signal,which reduces the calculation error attributed to the conventional Gaussian window function.Meanwhile,the frequency bandwidth selection rules for the linear regression of the amplitude ratio are given to further improve stability and accuracy.First,the feasibility and influencing factors of the SR-ST method are studied through numerical testing and standard sample experiments.Second,artificial samples with different Q values are used to study the adaptability and stability of the SR-ST method.Finally,a further comparison between the new method and the conventional spectral ratio method(SR)is conducted using rock field samples,again addressing stability and accuracy.The experimental results show that this method will yield an error of approximately 36%using the conventional Gaussian window function.This problem can be solved by adding the time window factors to the Gaussian window function.The frequency bandwidth selection rules and mean slope value of the amplitude ratio used in the SR-ST method can ensure that the maximum error of different Q values estimation(Q>15)is less than 10%.
基金Natural Science Foundation of Heilongjiang Province (E0221)Commonweal Foundation of the Ministry of Science and Technology of China (2001DIB20098).
文摘Based on 266 strong ground motion records, an attenuation relationship was developed for both absolute and relative input energy spectra. The comparison of the two kinds of input energy spectra constructed from the attenuation relationship was made in this paper. The results show that there is little difference between the absolute input energy spectra and relative input energy spectra at the periods of 0.5-1.0 s for elastic systems and at the period of 0.5 s for inelastic systems. The absolute input energy spectra are much larger than relative input energy spectra in very short period range but some less than relative input energy spectra in long period range. It is also found that the ductility factor has a significant effect on both absolute and relative input energy spectra. The absolute input energy spectra increase with the increasing of ductility factor in the period range of less than 0.3 s but decrease in the period range of larger than 0.3 s. The absolute input energy spectra for different ductility factor are almost equivalent at the period about 0.3 s, but for relative input energy spectra, the period is about 0.5 s. The effect of ductility on the relative input energy spectra in the short period range is much larger than that on the absolute input energy spectra, especially on the softer site class.
基金supported by the Scientific Institute, Rabat, Morocco
文摘We investigate attenuation scattering and loss properties in Souss basin(SW of High-Atlas) as a transition zone between the High and Anti Atlas ranges. This district consists in a thinned crustal patch with shallow seismicity and loose sedimentary trenches that perform an important contribution to augment seismic attenuation. So far, no coda waves approach in our knowledge have been used to draw satisfying outputs about the attenuation properties in the region. Therefore, this update suggests to correlate the lateral changes of seismic attenuation to different characteristics and asperities i.e. seismic activity,crustal age and thickness, heat flow, and ground deformation rate. To do so, we analysed coda waves derived from waveform data of more than 23 local earthquakes from seven broadband seismometers recorded during 2010 e2012 period. As a starter, we utilized the backscattering model which defines theseismic attenuation as inversely proportional to quality factor by the equation A ?1=. QQcestimates c were deducted at various central frequency bands 1.5, 3.0, 6.0, 9.0, 12.0 and 18.0 Hz according to different lapses times. The estimated average frequency dependence quality factor gives relation Qc? 120 f1;01,while the average Qcvalues vary from 149 at 1.5 Hz to 1895 at 18 Hz central frequencies. We observed an intimate dependence between quality factor and frequency ranges, which reflects the complexity of geological/geophysical pattern in the Souss basin and the presence of a variety of heterogeneities within the underlying crust.
基金National Natural Science Foundation of China(50468003)State 973 Project(2002 CB412706).
文摘In this paper, according to the relationship of observation spectrum with source spectrum, travel-path attenuation factor and site effect, we use the digital seismic data of moderate-small earthquakes to invert the soft rock site effect and S wave inelastic attenuation under the constraint of site effect, and determine the parameters of path and site. The parameters obtained by this method exclude the topographic effect of seismic stations, and truly reflect the seismic effect of free soft rock sites and the S wave inelastic attenuation in the studied region. The average soft rock site effect is about 1.5 times in the frequency domain of 2-4 Hz and the S wave quality factor is obtained as Qs=278f0.346, which can be directly applied to the stochastic modeling of ground motions in the studied region.
基金a part of author’s M.Sc Research under the project:‘‘Strengthening of Earthquake Engineering Center’’,funded by Higher Education Commission,Government of Pakistan
文摘An inversion method was applied to crustal earthquakes dataset to find S-wave attenuation characteristics beneath the Eastern Tohoku region of Japan. Accelerograms from 85 shallow crustal earthquakes up to 25 km depth and magnitude range between 3.5 and 5.5 were analyzed to estimate the seismic quality factor Qs. A homogeneous attenuation model Qs for the wave propagation path was evaluated from spectral amplitudes, at 24 different frequencies between 0.5 and 20 Hz by using generalized inversion technique. To do this, non-parametric attenuation functions were calculated to observe spectral amplitude decay with hypocentral distance. Then, these functions were parameterized to estimate Qs. It was found that in Eastern Tohoku region, the Qs frequency dependence can be approximated with the function 33 f 1.22 within a frequency range between 0.5 and 20 Hz. However, the frequency dependence of Qs in the frequency range between 0.5 and 6 Hz is best approximated by Qs （f） = 36 f 0.94 showing relatively weaker frequency dependence as compared to the relation Qs （f） = 6 f^ 2.09 for the frequency range between 6 and 15 Hz. These results could be used to estimate source and site parameters for seismic hazard assessment in the region.
文摘The frequency-dependent characteristics of P- and S-wave attenuation in the upper crust of NW Himalayas have been estimated using local earthquakes for a frequency range of 1.5 to 18 Hz. A total of 43 local events of magnitude 2.1 - 4.8, mostly from the vicinity of Main Boundary Thrust (MBT) and Main Central Thrust (MCT) have been used in the analysis. The extended coda normalization methods were applied to estimate the quality factors for P- waves (QP) and S-waves (QS) and the single back-scattering model has been used earlier (Kumar et al. [1]) to determine the quality factor for coda waves (QC). The observed quality factors QP and QS is strongly frequency dependent and the estimated average frequency dependent relation is given by QP = (97 ± 3)f (1.06 ± 0.06) and QS = (127 ± 6)f (0.96±0.06) respectively for P- and S-waves. A comparison of QS estimated in this study and QC previously reported shows that QC > QS for entire frequency range. This indicates the enrichment of coda waves and the importance of scattering attenuation to the attenuation of S-waves in the study region infested with faults and fractures. The ratio QS/QP is found to be greater than unity for the entire frequency range indicating that the body waves from source to station paths crossed a crustal volume with dry and rigid rocks. The frequency dependent relations developed in this study can be very useful to ground motion modeling which in turn is required in the seismic hazard assessment of the region.
基金This research was supported by the National Natural Science Foundation of China(No.42274141)Science Foundation of China University of Petroleum,Beijing(No.2462020YXZZ007).
文摘Dispersion and attenuation analysis can be used to determine formation anisotropy induced by fractures,or stresses.In this paper,we propose a nonparametric spectrum estimation method to get phase dispersion characteristics and attenuation coefficient.By designing an appropriate vector filter,phase velocity,attenuation coefficient and amplitude can be inverted from the waveform recorded by the receiver array.Performance analysis of this algorithm is compared with Extended Prony Method(EPM)and Forward and Backward Matrix Pencil(FBMP)method.Based on the analysis results,the proposed method is capable of achieving high resolution and precision as the parametric spectrum estimation methods.At the meantime,it also keeps high stability as the other nonparametric spectrum estimation methods.At last,applications to synthetic waveforms modeled using finite difference method and real data show its efficiency.The real data processing results show that the P-wave attenuation log is more sensitive to oil formation compared to S-wave;and the S-wave attenuation log is more sensitive to shale formation compared to P-wave.
基金This work was carried out as part of a Ph.D.research at the University of Houston.We thank Saudi Aramco for funding the research and providing the seismic data.We thank Dr.Carl Reine from Sound QI for providing the PSQI code.The Center of Wave Phenomenon(CWP)Seismic Unix programs TRIMODEL and TRISEIS were used to generate the synthetic seismic data.We thank Dr.Hao Hu for his comments and the anonymous reviewers for their reviews and suggestions.
文摘Accurately estimated interval attenuation(1/Q)values have several applications,such as in quantitative interpretation and seismic resolution enhancement.Although Q values can be estimated by measuring the spectral ratio between seismic reflections from a target and a reference reflector,the results are influenced by factors such as overburden inhomogeneities.Here,we quantitatively analyze the overburden influence on interval Q estimations using the spectral ratio method,time-space domain prestack Q inversion(PSQI),andτ-p domain PSQI.We compare these three methods using a synthetic dataset and a field dataset acquired onshore the Arabian Peninsula.Synthetic seismic gathers are generated from a three-layer model with a low-Q inclusion in the first layer to mimic overburden inhomogeneity.The fi eld data are preconditioned image gathers from a producing oil fi eld.The synthetic data test shows that the small low-Q body produces a considerable error in estimated Q values.The smallest error(i.e.,13.3%)is in theτ-p domain PSQI result.Theoretically,τ-p domain PSQI could obtain more accurate Q values when there are overburden infl uences because of the simultaneous inversion scheme and the application in theτ-p domain.The fi eld data application also illustrates that theτ-p domain PSQI produces reasonable interval Q values.Our measured Q values are also comparable with the Q values estimated from hydrocarbon saturated carbonate reservoirs.
文摘To answer the queries concerning penetrability of ~1 μT, physiologically patterned, time-varying magnetic fields through the cranium, the proportions of attenuation through thicknesses and densities of ~3 times that of the human skull were measured directly. There was no reduction in the intensity of the magnetic field when two 2 cm thick dried pine boards (4.3 × 103 kg·m-3) were placed between the pairs of solenoids separated by the approximate width of the skull. Although volumes of water containing intracellular concentrations of ions did not attenuate the field intensity, placement of 290 cm2 of 2 mm sheets of duct metal reduced the amplitude by 25%. Spectra comparisons showed a clear congruence in profiles between direct measurement of the applied field and the original computer-generated pattern. These results indicate there is little validity to claims that weak, time-varying magnetic fields applied in this manner are eliminated or significantly attenuated by the human skull.
