PubMed · 4756436
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M S Feld, V S Letokhov. 1973. Laser spectroscopy.. https://doi.org/10.1038/scientificamerican1273-69
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Heavy-gas dispersion of practical interest is usually cold gas dispersion with the enthalpy deficit as the main cause of the density effect. New analysis of existing field experiment data suggests that heat transfer from the ground sometimes reduces this thermally induced density effect considerably. The limited heat capacity of the ground implies that heat transfer to a gas plume must disappear eventually, and our interpretation of Desert Tortoise measurements indicates that the surface heat flux decreased by 38% during a 3-min long release period.
PURPOSE: To report a modification in the design of bed spectacles to provide an aid for patients who undergo face-down positioning after vitrectomy with gas-fluid exchange and postoperative gas tamponade. METHODS: New equipment design. Bed spectacles that use prisms to move the image 90 degrees around the horizontal meridian were modified by rotating the prisms in the frame 180 degrees and adding nosepads and cable temples. The spectacles were given to 12 patients for use during postoperative face-down positioning. A questionnaire was used to evaluate the helpfulness of the spectacles during face-down positioning. RESULTS: Patients ranked the spectacles as "helpful" to "very helpful" with a mean and SD of 8.3+/-1.6 on a scale of 1 to 10, where 1 was "a hindrance" and 10 was "very helpful." Patients wore the spectacles an average of 5.7+/-4.5 hours a day (range, 1.5 to 15 hours). CONCLUSION: Modified bed spectacles appear to be a portable aid to patients who undergo face-down positioning while sitting, standing, or prone.
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