Digital elevation model uncertainty and hazard analysis using a geophysical flow model

This paper describes a new methodology to quantify the variation in the output of a computational fluid dynamics model for block and ash flows, when the digital elevation model (DEM) of the terrain and other inputs are given as a range of possible values with a prescribed uncertainty. Integrating these variations in the possible flows as a function of input uncertainties provides well-defined hazard probabilities at specific locations, i.e. a hazard map. Earlier work provided a methodology for assessing hazards based on variations in flow initiation and friction parameters. This paper extends this approach to include the effect of terrain error and uncertainty. The results are based on potential flows at Mammoth Mountain, CA, and Galeras Volcano, Colombia. The analysis establishes the soundness of the approach and the effect of including the uncertainty in DEMs in the construction of probabilistic hazard maps.

Computer-assisted mapping of pyroclastic surges

Volcanic hazard maps of surge boundaries and deposit thickness can be created by using a simplified eruption model based on an "energy line" concept of pyroclastic surge and flow emplacement. Computer image-processing techniques may be used to combine three-dimensional representations of the energy relations of pyroclasts moving under the influence of gravity (defined by an "energy cone") with digital topographic models of volcanoes to generate theoretical hazard maps. The deposit boundary and thickness calculated for the 18 May 1980 eruption of Mount St. Helens are qualitatively similar to those actually observed.

Inner ear barotrauma from scuba diving

Inner ear barotrauma among scuba divers is believed to be caused by any of three conditions: a hemorrhage in the inner ear, a tear of the labyrinthine membrane, or a perilymphatic fistula. These injuries may occur concurrently or separately. Hemorrhage and membrane rupture are managed conservatively, while fistula requires surgical repair. In this report, we describe three cases of inner ear barotrauma in scuba divers. We also discuss the proposed etiologies of this injury and the controversy over whether or not divers who have suffered an inner ear trauma can safely resume scuba diving. Although the older literature clearly suggests otherwise, we believe that scuba divers who completely recover from inner (or middle) ear barotrauma may return to diving as long as they exercise caution and care.

Endoscopic sinus surgery complications in residency

Otolaryngology has seen a rapid proliferation of functional endoscopic sinus surgery, and there is variability in the teaching of the procedure, in part because of the seriousness of the complications. A retrospective review of 106 consecutive cases was conducted at a teaching program to evaluate complications. Complication rates were combined and compared with the reported complication rates of other teaching programs and practicing otolaryngologists. The complication rate in our program was 13.9%; all were minor complications. This compared favorably with the rates of other programs (6% to 29%). The combined complication rate for residency training programs (16.6%) was significantly greater than the nonresident complication rate (10.5%). When divided into major and minor complications, the resident minor complication rate (15.9%) was significantly greater than the nonresident rate (8%), yet the major complication rates were significantly less for the resident group (0.7%) than for the nonresident group (2.5%). In addition, complications were significantly greater when procedures were performed under general anesthesia as compared with local anesthesia, and estimated blood loss was significantly greater under general anesthesia.

KTP laser excision of a soft palate squamous cell carcinoma: a case report

Squamous cell carcinoma of the soft palate is an infrequently seen tumor of the oral cavity. The use of the KTP laser in the treatment of a 52-year-old man with a T2N0M0 soft palate carcinoma is reported. The natural history and treatment of this entity is reviewed. The application of tumor thickness as related to therapy of the neck and prognosis is commented on. Use of the KTP laser for resection of oral cavity lesions is felt to be a technological improvement beneficial to both patients and practitioners.

Hydrovolcanic Explosions: The Systematics of Water-Pyroclast Equilibration

The initial contact of external water with erupting magma and the mass ratio of water to magma govern the development of hydrovolcanic phenomena. The phase relations of water within the runout system and the separation of vapor or liquid from the pyroclasts explain gradational transitions between some pyroclastic flows, base surges, mud hurricanes, mudflows, and sheetfloods.

Early Miocene Subglacial Basalts, the East Antarctic Ice Sheet, and Uplift of the Transantarctic Mountains

Subglacially erupted volcanic rocks from Mount Early and Sheridan Bluff, Antarctica, yield whole-rock potassium-argon dates and argon-40/argon-39 release spectra of Early Miocene age. Field associations suggest the existence of the East Antarctic ice sheet and significant uplift of the Transantarctic Mountains by that time.