Study on Multi-density Contrast Agent Fillers of Duct Casting Based on CT Three-Dimensional Reconstruction

The three-dimensional visualization model of human body duct is based on virtual anatomical structure reconstruction with duct angiography,which realizes virtual model transferred from two-dimensional,planar and static images into three-dimensional,stereoscopic and dynamic ones repectively.In recent years,the multi-duct segmentation and division of the same specimen（or organ） is the focus of attention shared by surgeons and clinical anatomists.On the basis of 4.22 g/cm3 body bone density,this study has screened out metal oxide contract agent with different density for infusion and modeling,as well as compared and analyzed the effects of three-dimensional image of CT virtual bronchoscopy（CTVB）,three-dimensional image of CT maximum intensity projection and three-dimensional model.This experiment result showed synchronously infusing multi-duct of same specimen（or organ） with contrast agent in different densities could reconstruct three-dimensional models of all ducts once only and adjust threshold to develop single or multiple ducts.It was easier to segment and observe the duct structure,anastomosis,directions and crossing in different parts,which was beyond comparison with three-dimensional image of CTVB.Although the existing three-dimensional duct reconstruction techniques still cannot be applied in living bodies temporarily,this study focused on a creative design of ducts segmentation in different density,which proposed a new experimental idea for developing multi-duct three-dimensional model in living body in the future.It will play a significant role in disease diagnosis and individual design in surgical treatment program.Therefore,this study observes the three-dimensional status of human duct with the application of contrast agent fillers in different density,combined with three-dimensional reconstruction technology.It provides an innovative idea and method for constructing three-dimensional model of digital multi-duct specimen,and the ultimate goal is to develop the digitized virtual human and precise medical treatment better and faster.

Constraining Shear Wave Velocity and Density Contrast at the Inner Core Boundary with PKiKP/P Amplitude Ratio

Shear velocity and density contrast across the inner core boundary are essential for stud- ying deep earth dynamics, geodynamo and geomagnetic evolution. In previous studies, amplitude ratio of PKiKP/PcP at short distances and PKiKP/P at larger distances are used to constrain the shear veloc- ity and density contrast, and shear velocity in the top inner core is found to be substantially smaller than the PREM prediction. Here we present a large dataset of PKiKP/P amplitude ratio measured on 420 seismic records at ILAR array in Alaska for the distance range of 800-90~, where the amplitude ra- tio is sensitive to shear velocity and density contrast. At high frequency （up to 6 Hz）, mantle attenuation is found to have substantial effects on PKiKP/P. After the attenuation effects are taken into account, we find that the density contrast is about 0.2-1.0 g/cm3, and shear velocity of inner core is 3.2-4.0 km/s, close to the PREM （Preliminary Reference Earth Model） prediction （0.6 g/cm3 and 3.5 kin/s, respec- tively）. The relatively high shear velocity in inner core does not require large quantities of defects or melts as proposed in previous studies.

Research on the scatter features of the PKiKP/PcP amplitude ratio and the inner core boundary density contrasts beneath Northeast Asia

Quantifying the density contrasts of the Earth’s inner core boundary(ICB)is crucial to understand core-mantle coupling and the generation of the geodynamo.The PKiKP/PcP amplitude ratio is commonly used to obtain the density contrast at the ICB,but its applications are limited by scattered observed data.In this study,we selected the PKiKP and PcP phases reflected at the same region of inner-core and core-mantle boundaries beneath Northeast Asia from different earthquakes for the first time,and the observations suggested that the PKiKP/PcP amplitude ratio is widely scattered.We also compared the PKiKP and PcP amplitudes,which demonstrated that the scatter cannot be attributed only to ICB anomalies but might also arise from raypath differences and heterogeneities throughout the crust and mantle.By fitting the observed PKiKP/PcP amplitude ratio,we obtained a density contrast of approximately 0.65 g cm^(-3) and a compressional velocity contrast of approximately 0.87 km s^(-1) at the ICB beneath Northeast Asia.The larger contrast values indicate the possible occurrence of local crystallization occurring at the inner core surface.

Imaging Rock Density Distribution beneath Liwa Fracture Zone in the Southern Part of the Great Sumatran Fault System, Indonesia

We have imaged rock density distribution beneath Liwa fracture zone in the southern part of the the Sumatran Fault Zone by modelling and inverting Bouguer gravity data in two-and three-dimensional environments, respectively. The purpose of this study is aimed to figure out the subsurface distribution of rock densities associated with subsurface basement structure representing the evidence of trans-tensional tectonic product in the SF. In the gravity modeling, to eliminate distortions to the measured gravity values before modelling and inverting the data, Bouguer anomalies obtained in field measurements are reduced to the horizontal plane of z = +800 m as a representation of the average elevation in Liwa. For the inversion, we used algorithm implementing depth-and minimum volume weighting parameters in order to obtain a smooth model with better vertical resolution. The two-dimensional models show clearly surface topography of the basement rocks and the presence of normal faults. The reduced Bouguer anomaly of +800 m elevation shows the presence of structural lineaments extending primarily in a northwest-southeast direction, parallel to Sumatran Fault Zone and older graben faults showing a negative flower structure. From the three-dimensional inversion, the model illustrates an increase of density contrast, lower values being found near the surface and higher values in the deeper parts. The lower density contrast of 0.15 to 0.3 g/cm3 found in the rock groups at depths of 2 km and less is characteristic of relatively homogeneous and poorly compacted rocks. Rocks with moderate to high density contrast (>1.0 g/cm3) are recognized at depths of over 2 km. This model suggests a change of basement morphology as a function of depth, and delineates structural lineaments extending in northwest-southeast direction. This study supports the previous thought that Liwa area is underlain by graben structures, formed by trans-tensional tectonic events. Higher-density Tertiary volcanic breccia and lower-density Quaternary volcanic products of the Ranau Formation form the basement rocks and the overlying younger sediments, respectively.

Implications on Gravity Anomaly Measurements Associated with Different Lithologies in Turkana South Subcounty

The use of gravity data has demonstrated capability for monitoring lithological changes on a large scale as a consequence of differentiating basement and sedimentary of buried valleys. Gravity anomalies are associated with lateral contrasts in density and therefore deformation by faulting or folding will be manifested if accompanied by lateral density changes, otherwise, the vice versa is true. The study’s objective is to evaluate the effectiveness of gravity method in establishing different lithologies in an area. The study has revealed that regional anomaly gravity map presents high anomalies in the Northern region in the NW-SE trend and low anomalies in the southern trend in NW-SE, while the residual anomaly gravity map shows different trends for the low and high gravity anomalies. The gravity anomalies are well interpreted in line with the lithologies of the study area rather than the deformation of the same lithologies. There are observed high values of gravity anomaly values (ranging from -880.2 to -501.2 g.u.) where there are eolian unconsolidated rocks overlying the basement compared to low gravity anomaly values (ranging from -1338.9 to -1088.7 g.u.) where the andesites, trachytes and phonolites overly the basement. The different regional gravity anomalies relate well with different rock densities in the study area along the line profile for radially averaged power spectrum. The gravity highs are noted in the eastern point and are associated with andesites, trachytes, basalts and igneous rocks, while the gravity lows are associated with sandstone, greywacke, arkose, and eolian unconsolidated rock. The utilization of the information from the Power spectrum analysis demonstrates that the depth to the deepest basement rock is 12.8 km which is in the eastern flank, while the shallowest to the basement of 1.1 km to the western flank.

Combined Moho Parameters Determination Using CRUST1.0 and Vening Meinesz-Moritz Model

According to Vening Meinesz-Moritz （VMM） global inverse isostatic problem, either the Moho density contrast （crust-mantle density contrast） or the Moho geometry can be estimated by solv- ing a non-linear Fredholm integral equation of the first kind. Here solutions to the two Moho parame- ters are presented by combining the global geopotential model （GOCO-03S）, topography （DTM2006） and a seismic crust model, the latter being the recent digital global crustal model （CRUST1.0） with a resolution of 1°×1°. The numerical results show that the estimated Moho density contrast varies from 21 to 637 kg/m3, with a global average of 321 kg/m^3, and the estimated Moho depth varies from 6 to 86 km with a global average of 24 km. Comparing the Moho density contrasts estimated using our least-squares method and those derived by the CRUST1.0, CRUST2.0, and PREM models shows that our estimate agrees fairly well with CRUST1.0 model and rather poor with other models. The estimated Moho depths by our least-squares method and the CRUST1.0 model agree to 4.8 km in RMS and with the GEMMA1.0 based model to 6.3 km.