Brian J Mitchell – författare

In this issue of�Surgical�Clinics,�guest�editors�Drs.�Brian J. Mitchell and Kyle Tubbs�bring�their�considerable expertise to the topic of�Head and Neck Surgery.�Top experts in the field�address�a wide variety of topics, including�head and neck cancer, esophageal dysphagia, salivary glands, thyroid nodules, and oral cancer.�Also included is a timely social media article on�"Guarding Your Online Reputation.�

Variations in seismic Q are sensitive to a much greater extent than are seismic velocity variations on factors such as temperature, fluid content, and the movement of solid state defects in the earth. For that reason an understanding of Q and its variation with position in the earth and with time should provide information in earth's tectonic evolution, as well as on aspects of its internal structure. Progress in understanding Q has suffered from difficulty in obtaining reliable amplitude data at global and temporary stations. Moreover, laboratory determinations of Q, until recently, were most often made at frequencies much higher than those measured by seismologists for waves propagating through the earth. Recent advances in seismic station distribution and quality, as well as in methodology at both high and low fequencies, have greatly improved the quality of observational data available to seismologists from global stations. Concurrent advances have been made in measuring Q using laboratory samples at frequencies that pertain to the earth and in theoretical understanding of seismic wave attenuation. Papers of this volume present new information on Q in the earth from several perspectives: methodology, results from global and regional observations of both body and surface waves, laboratory measurements, and theoretical understanding. The editors believe that we have reached a new threshold in Q studies and that advances in data quality and methodology will spur increased interest in this difficult, but interesting field.

Successful monitoring of a CTBT requires that we detect and identify all nuclear explosions. Since many events of concern will be too small to be detected teleseismically, this capability requires the use of regional-distance seismograms. The complexity of regional seismograms presents many technical challenges for a monitoring program. This issue focuses on problems associated with regional wave propagation through complex media. It includes papers that investigate regional variations of elastic and anelastic properties of Eurasia, the blockage of regional phases by sedimentary basins, methods for modeling regional wave propagation and for calibrating seismic wave paths in order to extract amplitude variations and source parameters. These papers illustrate the research and development necessary for acquiring an understanding of regional wave propagation which in turn provides the foundation for operational tools used to monitor a CTBT.