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We did not find a consistent pattern of ventilation change as a function of radiation dose. Pretreatment ventilation was significantly lower for lobes that contained tumor, due to occlusion of the central airway. The weekly lobe ventilation data indicated that when tumor volume shrinks, ventilation increases, and when the thoracic anatomy is not visibly changed, ventilation is likely to remain unchanged.

In a previous study published in this journal, the authors developed a comprehensive methodology for modelling the shear wave velocity profile in crustal rock, for purposes of seismic hazard assessment. The derived shear wave velocity profile was used to estimate the amplification and attenuation mechanisms in the transmission of seismic waves. The ability to conduct seismic hazard assessments in regions of low and moderate seismicity is greatly enhanced by this new modelling approach, given that developing a local attenuation model based on curve-fitting strong motion data is generally not feasible under such conditions. This paper reports a follow-up study conducted to evaluate the significance of near-surface attenuation in bedrock (as distinct from attenuation in unconsolidated soft soil sediments). The κ κ κ κ parameter is used to characterize the extent of this attenuation mechanism. Empirical correlations of κ κ κ κ with two forms of near-surface shear wave velocity parameter in crustal rock have been developed, employing information obtained from global sources in conjunction with that from local studies. The resulting development of two simple equations to predict median values of κ κ κ κ as functions of readily available shear wave velocity parameters represents the key outcome of this study. Applications of the proposed empirical approaches to determine κ κ κ κ have been provided, taking Hong Kong and Melbourne as case studies to illustrate different aspects of the proposed methodology. Consistency between the results obtained by the two recommended approaches has thereby been demonstrated.

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The magnetorheological (MR) damper is considered to be one of the most promising semi-active control devices for reduction of structural vibration. Due to the damper's nonlinear characteristic, its inverse dynamics model is difficult to obtain. In this paper, a simplified approach, namely the Simplified Inverse Dynamics (SID) model, has been developed for both the Bingham plasticity model and the Bouc-Wen hysteresis model. SID models have then been used to calculate the optimal fluid yield stress or input current, in order to realize the desirable control forces obtained from various optimal control algorithms. For each model, a piston velocity feedback (PVF) algorithm and a damper force feedback (DFF) algorithm have been formulated. The proposed model has been shown to be applicable to both small-scale and large-scale MR dampers. Also, different configurations of MR dampers, such as, different dimension, coil resistance, type of MR fluid, have been employed to show the generic nature of SID model. The effectiveness of force tracking using SID model has been demonstrated through a series of numerical simulations. A multi-storey frame structure with MR damper-brace systems, using a large-scale 20-ton MR damper, has been adopted. Numerical results show that the MR damper with the proposed SID model can produce forces very close to the optimal control forces, and that the response reduction is very close to the case of fully active control. Also, equally high accuracy of force tracking for different shaking levels and frequency contents of ground motions can be observed. The results demonstrate that SID model can be a simple, yet effective, tool for both research and application purposes.

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SUMMARYThe seismological model was developed initially from the fundamental relationship between earthquake ground motion properties and the seismic moment generated at the source of the earthquake. Following two decades of continuous seismological research in the United States, seismological models which realistically account for both the source and path e!ects on the seismic shear waves have been developed and their accuracy rigorously veri"ed (particularly in the long and medium period ranges). An important "nding from the seismological research by Atkinson and Boore and their co-investigators is the similarity of the average frequency characteristics of seismic waves generated at the source between the seemingly very di!erent seismic environments of Eastern and Western North America (ENA and WNA, respectively). A generic de"nition of the average source properties of earthquakes has therefore been postulated, referred to herein as the generic source model.Further, the generic &hard rock' crustal model which is characteristic of ENA and the generic &rock' crustal model characteristic of WNA have been developed to combine with the generic source model, hence enabling simulations to be made of the important path-related modi"cations to ground motions arising from di!erent types of crustal rock materials. It has been found that the anelastic contribution to whole path attenuation is consistent between the ENA and WNA models, for earthquake ground motions (response spectral velocities and displacements) in the near and medium "elds, indicating that di!erences in the ENA and WNA motions arise principally from the other forms of path-related modi"cations, namely the mid-crust ampli"cation and the combined e!ect of the upper-crust ampli"cation and attenuation, both of which are signi"cant only for the generic WNA &rock' earthquake ground motions.This paper aims to demonstrate the e!ective utilization of the latest seismological model, comprising the generic source and crustal models, to develop a response spectral attenuation model for direct engineering applications. The developed attenuation model also comprises a source factor and several crustal (wavepath modi"cation) component factors, and thus has also been termed herein the component attenuation model (CAM). Generic attenuation relationships in CAM, which embrace both ENA and WNA conditions, have been developed using stochastic simulations. The crustal classi"cation of a region outside North America can be based upon regional seismological and geological information. CAM is particularly useful for areas where local strong motion data are lacking for satisfactory empirical modelling. In the companion paper entitled &response spectrum modelling for rock sites in low and moderate seismicity regions combining velocity, displacement and acceleration predictions', the CAM procedure has been incorporated into a response spectrum model which can be used to e!ectively de"ne the seismic hazard of bedrock sites in low and moderate seismicity regions. This paper and the co...

Purpose:To assess the reproducibility of computed tomographic (CT) perfusion measurements in liver tumors and normal liver and effects of motion and data acquisition time on parameters. Materials and Methods:Institutional review board approval and written informed consent were obtained for this prospective study. The study complied with HIPAA regulations. Two CT perfusion scans were obtained 2-7 days apart in seven patients with liver tumors with two scanning phases (phase 1: 30-second breathhold cine; phase 2: six intermittent free-breathing cines) spanning 135 seconds. Blood fl ow (BF), blood volume (BV), mean transit time (MTT), and permeability-surface area product (PS) for tumors and normal liver were calculated from phase 1 with and without rigid registration and, for combined phases 1 and 2, with manually and rigid-registered phase 2 images, by using deconvolution modeling. Variability was assessed with within-patient coeffi cients of variation (CVs) and Bland-Altman analyses.