Numerical modeling of elastic-wave scattering by near-surface heterogeneities

In land seismic data, scattering from surface and near-surface heterogeneities adds complexity to the recorded signal and masks weak primary reflections. To understand the effects of near-surface heterogeneities on seismic reflections, we simulated seismic-wave scattering from arbitrary-shaped, shallow, subsurface heterogeneities through the use of a perturbation method for elastic waves and finite-difference forward modeling. The near-surface scattered wavefield was modeled by looking at the difference between the calculated incident (i.e., in the absence of scatterers) and the total wavefields. Wave propagation was simulated for several earth models with different near-surface characteristics to isolate and quantify the influence of scattering on the quality of the seismic signal. The results indicated that the direct surface waves and the upgoing reflections were scattered by the near-surface heterogeneities. The scattering took place from body waves to surface waves and from surface waves to body waves. The scattered waves consisted mostly of body waves scattered to surface waves and were, generally, as large as, or larger than, the reflections. They often obscured weak primary reflections and could severely degrade the image quality. The results indicated that the scattered energy depended strongly on the properties of the shallow scatterers and increased with increasing impedance contrast, increasing size of the scatterers relative to the incident wavelength, decreasing depth of the scatterers, and increasing attenuation factor of the background medium. Also, sources deployed at depth generated weak surface waves, whereas deep receivers recorded weak surface and scattered body-to-surface waves. The analysis and quantified results helped in the understanding of the scattering mechanisms and, therefore, could lead to developing new acquisition and processing techniques to reduce the scattered surface wave and enhance the quality of the seismic image.Saudi AramcoMassachusetts Institute of Technology. Earth Resources Laborator

A Pre-Landing Assessment of Regolith Properties at the InSight Landing Site

This article discusses relevant physical properties of the regolith at the Mars InSight landing site as understood prior to landing of the spacecraft. InSight will land in the northern lowland plains of Mars, close to the equator, where the regolith is estimated to be ≥3--5 m thick. These investigations of physical properties have relied on data collected from Mars orbital measurements, previously collected lander and rover data, results of studies of data and samples from Apollo lunar missions, laboratory measurements on regolith simulants, and theoretical studies. The investigations include changes in properties with depth and temperature. Mechanical properties investigated include density, grain-size distribution, cohesion, and angle of internal friction. Thermophysical properties include thermal inertia, surface emissivity and albedo, thermal conductivity and diffusivity, and specific heat. Regolith elastic properties not only include parameters that control seismic wave velocities in the immediate vicinity of the Insight lander but also coupling of the lander and other potential noise sources to the InSight broadband seismometer. The related properties include Poisson’s ratio, P- and S-wave velocities, Young’s modulus, and seismic attenuation. Finally, mass diffusivity was investigated to estimate gas movements in the regolith driven by atmospheric pressure changes. Physical properties presented here are all to some degree speculative. However, they form a basis for interpretation of the early data to be returned from the InSight mission.Additional co-authors: Nick Teanby and Sharon Keda

An investigation of how volatile financial analyst recommendations may affect managerial behaviour and financial reporting quality

This study investigates how the volatility in analyst buy recommendations in the UK may affect managerial behaviour. It examines whether the adoption of earnings manipulation and other opportunistic behaviours, such as managing the reporting tone of press releases, financial statement complexity and CEO overconfidence, may lead to volatile buy recommendations. This study shows that the use of earnings manipulation, especially when companies' current performance differs from the forecast, is likely to result in volatile buy recommendations. Volatile buy recommendations are linked to greater financial statement complexity and higher tonal disagreement between press releases and media articles. Analysts issue less buy recommendations when financial statements are complex or when overconfident CEO behaviour is reported. Companies with volatile buy recommendations are more likely to experience greater stock price crash risk, especially when accompanied by CEO overconfidence and tonal disagreement. Copyright © 2022 Inderscience Enterprises Ltd

Scalp Dermatophyte Carriage in Pregnant, Pre-, and Postmenopausal Women: A Comparative Study Using the Hairbrush and Cytobrush Methods of Sample Collection

PubMedID: 21063784Tinea capitis is a dermatophyte infection of the scalp that is most often seen in prepubescent children. In this investigation, we examined the prevalence of tinea capitis and symptom-free colonization of the scalp with dermatophytes in 786 pre- and postmenopausal women aged 12-84 years. Scalp samples were collected from all participants by cytobrush or hairbrush, and cultures were then grown from these samples on Sabouraud glucose agar. No participant was diagnosed with tinea capitis; however, one 43-year-old patient (0.1%) was positive for a "scalp carriage" related to anthropophilic Trichophyton rubrum, as detected using a hairbrush. The internal transcribed spacer (ITS) regions of the isolate were sequenced, and the assembled DNA sequences were examined using the basic BLAST (nucleotide-nucleotide) software of the National Center for Biotechnology Information Web database. This patient was followed up without any antimycotic treatment, and after 4 weeks, mycological clearance was documented. In addition, the contacts and environment at home were screened, where all fungal cultures were sterile. To the best of our knowledge, this study is the first report of a "scalp carriage" related to a cosmopolitan fungus, T. rubrum. © 2010 Springer Science+Business Media B.V.TF2010BAP14Acknowledgments This study was supported by the Research Fund of Cukurova University (Project No: TF2010BAP14). We gratefully acknowledge Prof Dr G. Sybren de Hoog’s (Centraal-bureau voor Schimmelcultures, Utrecht, The Netherlands) kind cooperation and confirmation of the isolate examined in this study