One-Way Wave Propagators For Velocity Analysis On Curvilinear Coordinates

Due to present computational limitations, migration by the one-way wave equation remains an integral tool in seismic exploration. For the realistic interpretation of common image point gathers, it is necessary that migration be free from artifacts from caustics and turning waves. In order to permit situations where turning waves occur, we perform our migration on specially chosen curvilinear coordinates where waves do not travel horizontally. We present an implementation of the curvilinear one-way wave equation using a rational approximation and discuss its application in migration velocity analysis, as well as transmission and reflection tomography

Wave-Equation Reflection Tomography: Annihilators and Sensitivity Kernals

In seismic tomography, the finite frequency content of broad-band data leads to interference effects in the process of medium reconstruction, which are ignored in traditional ray theoretical implementations. Various ways of looking at these effects in the framework of transmission tomography can be found in the literature. Here,we consider inverse scattering of bodywaves to develop a method of wave-equation reflection tomography with broad-band waveform data— which in exploration seismics is identified as a method of wave-equation migration velocity analysis. In the transition from transmission to reflection tomography the usual cross correlation between modelled and observed waveforms of a particular phase arrival is replaced by the action of operators (annihilators) to the observed broad-bandwave fields. Using the generalized screen expansion for one-way wave propagation, we develop the Fréchet (or sensitivity) kernel, and show how it can be evaluated with an adjoint state method. We cast the reflection tomography into an optimization procedure; the kernel appears in the gradient of this procedure.We include a numerical example of evaluating the kernel in a modified Marmousi model, which illustrates the complex dependency of the kernel on frequency band and, hence, scale. In heterogeneous media the kernels reflect proper wave dynamics and do not reveal a self-similar dependence on frequency: low-frequency wave components sample preferentially the smoother parts of the model, whereas the high-frequency data are—as expected—more sensitive to the stronger heterogeneity.We develop the concept for acoustic waves but there are no inherent limitations for the extension to the fully elastic case.TOTAL (Firm)National Science Foundation (U.S.) (grant EAR-0409816

Source-Indexed Migration Velocity Analysis with Global Passive Data

The reverse-time migration of global seismic data generated by free-surface multiples is regularly used to constrain the crustal structure, but its accuracy is to a large extent determined by the accuracy of the 3-D background velocity model used for wave propagation. To this improve the velocity model and hence the accuracy of the migrated image, we wish to apply the technique of migration velocity analysis (MVA) to global passive data. Applications of MVA in the active setting typically focus on o ffset- or angle-gather annihilation, a process that takes advantage of data redundancy to form an extended image, and then applies an annihilation operator to determine the success of image formation. Due to the nature of regional-scale passive seismic arrays, it is unlikely that the data in most of these studies will be su cient to form an extended image volume for use in annihilation-based MVA. In order to make use of the sparse and irregular array design of these arrays, we turn towards a shot-pro le moveout scheme for migration velocity analysis introduced by Xie and Yang (2008). In the place of extended image annihilation, we determine the success of the migration velocity model by using a weighted image correlation power norm. We compare pairs of images formed by migrating each teleseismic source by image cross-correlation in the depth direction. We look for a suitable background model by penalizing the amount of correlation power away from zero depth shift. The total weighted correlation power between source-pro le images is then used as the error function and optimized via conjugate gradient. We present the method and a proof-of-concept with 2-D synthetic data

Reverse-time migration-based reflection tomography using teleseismic free surface multiples

Converted and multiply reflected phases from teleseismic events are routinely used to create structural images of the crust–mantle boundary (Moho) and the elasticity contrasts within the crust and upper mantle. The accuracy of these images is to a large extent determined by the background velocity model used to propagate these phases to depth. In order to improve estimates of 3-D velocity variations and, hence, improve imaging, we develop a method of reverse-time migration-based reflection tomography for use with wavefields from teleseismic earthquakes recorded at broad-band seismograph arrays. Reflection tomography makes use of data redundancy—that is, the ability to generate numerous structural images of the subsurface with different parts of the wavefield. In exploration seismology (where it is known as migration velocity analysis) reflection tomography typically involves the generation of an extended image (e.g. offset- or angle-gathers), and the fitness of the background model is evaluated through the application of image-domain annihilators. In regional-scale passive source seismology, however, annihilation-based methods are inadequate because the sparse and irregular distribution of teleseismic sources is not likely to produce illumination over a sufficient range of angles. To overcome this problem we turn towards a source-indexed moveout scheme. Instead of extended image annihilation, we determine the success of the tomographic velocity model by cross correlating images produced with multiply scattered waves from different teleseismic sources. The optimal velocity model is the one that minimizes correlation power between windowed images away from zero depth shift. We base our inversion scheme on the seismic adjoint method and a conjugate gradient solver. For each image pair, the update direction is determined by correlations between downgoing wavefields with upgoing adjoint wavefields for both images. The sensitivity kernels used in this method is similar to those found in other forms of adjoint tomography, but their shapes are controlled by the spatial distribution of the error function. We present the method and a proof-of-concept with 2-D synthetic data

Prognostic factors in men with metastatic castration-resistant prostate cancer treated with cabazitaxel

Background: Treatment selection for men with metastatic castration-resistant prostate cancer (mCRPC) has become increasingly challenging with the introduction of novel therapies at earlier disease stages. The purpose of this study was to identify prognostic factors for overall survival (OS) and PSA response in patients with mCRPC treated with cabazitaxel. Results: 224 mCRPC patients were included in the current analysis. In multivariable analysis, WHO performance status, baseline hemoglobin, alkaline phosphatase and albumin were all significantly associated with OS. Hemoglobin and alkaline phosphatase were significantly associated with PSA response. Conclusions: This study identified prognostic factors for OS and PSA response of men with mCRPC treated with cabazitaxel. In an increasingly complicated treatment landscape with several treatment options available our findings might serve to estimate the chance of survival of men qualifying for treatment with second-line chemotherapy in daily practice. Furthermore, these data can be used to risk-stratify patients in clinical trials. Methods: We performed a post-hoc analysis of a randomized phase II trial of mCRPC patients treated with cabazitaxel. Cox and logistic regression models were used to investigate the influence of clinical and biochemical variables on OS and PSA response. Nomograms were developed to estimate the chance of PSA response and OS

The interplay between tamoxifen and endoxifen plasma concentrations and coagulation parameters in patients with primary breast cancer

Background: Tamoxifen is an effective treatment for primary breast cancer but increases the risk for venous thromboembolism. Tamoxifen decreases anticoagulant proteins, including antithrombin (AT), protein C (PC) and tissue factor (TF) pathway inhibitor, and enhances thrombin generation (TG). However, the relation between plasma concentrations of both tamoxifen and its active metabolite endoxifen and coagulation remains unknown. Methods: Tamoxifen and endoxifen were measured in 141 patients from the prospective open-label intervention TOTAM-study after 3 months (m) and 6 m of tamoxifen treatment. Levels of AT and PC, the procoagulant TF, and TG parameters were determined at both timepoints if samples were available (n = 53–135 per analysis). Levels of coagulation proteins and TG parameters were correlated and compared between: 1) quartiles of tamoxifen and endoxifen levels, and 2) 3 m and 6 m of treatment. Results: At 3 m, levels of AT, PC, TF and TG parameters were not associated with tamoxifen nor endoxifen levels. At 6 m, median TF levels were lower in patients in the 3rd (56.6 [33] pg/mL), and 4th (50.1 [19] pg/mL) endoxifen quartiles compared to the 1st (lowest) quartile (76 [69] pg/mL) (P=0.027 and P=0.018, respectively), but no differences in anticoagulant proteins or TG parameters were observed. An increase in circulating TF levels (3 m: 46.0 [15] versus 6 m: 54.4 [39] pg/mL, P &lt; 0.001) and TG parameters was observed at the 6 m treatment timepoint, while AT and PC levels remained stable.Conclusions: Our results indicate that higher tamoxifen and endoxifen levels are not correlated with an increased procoagulant state, suggesting tamoxifen dose escalation does not further promote hypercoagulability.</p

Avian Bornaviruses in Psittacine Birds from Europe and Australia with Proventricular Dilatation Disease

Birds with this disease display bornaviral antigen in neural and extraneural tissues