The PMC Turbo Experiment: Design, Development, and Results

In the middle and upper atmosphere, dynamics of scales from tens of meters to thousands of kilometers primary arise due to the influence of gravity waves propagating from lower altitudes. In order to understand the structure and variability of these regions of our planet's atmosphere, we must understand the propagation, influences, and dissipation of gravity waves. However, gravity waves and their influences are difficult to measure. Their largest and most observable effects occur in the remote mesosphere and lower thermosphere and the relevant spatial scales extend across many orders of magnitude. The EBEX group discovered a novel method to observe polar mesospheric clouds, which are a sensitive tracer of gravity waves and their associated dynamics. This discovery motivated the Polar Mesospheric Cloud Turbulence (PMC Turbo) experiment. Polar mesospheric clouds form an extremely thin but bright layer at roughly 80 kilometer altitude in which we can observe brightness fluctuations created by gravity wave dynamics and the resulting instabilities. PMC Turbo included seven pressure vessels, each of which contained an optical camera, hard drives, and computers that controlled the image capture, flight control, and communication with ground stations. The cameras captured spatial scales from gravity waves with wavelengths of roughly 10-100 kilometers, instability dynamics at scales from about 1-10 kilometers, and the fine structure at the inner scale of turbulence down to 20 meters. PMC Turbo flew at 38 kilometer altitude and remained afloat for nearly six days. During this time, it travelled from Esrange Space Center in Sweden to the Northwest Passage in Canada. Complementary data from other instruments provides additional atmospheric context to the PMC Turbo measurements. During flight, the PMC Turbo cameras captured images of polar mesospheric clouds tracing Kelvin-Helmholtz instabilities with a high signal-to-noise ratio. Kelvin-Helmholtz instabilities play major roles in energy dissipation and structure of geophysical fluids, and they have a close relationship with gravity waves. The PMC Turbo images include complicated interactions and secondary instabilities leading to turbulence. These dynamics provide insight into the atmospheric conditions and rate of energy dissipation in the mesosphere and lower thermosphere

Thoughts and Progress

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/75183/1/j.1525-1594.1999.06248.x.pd

The ideal home hemodialysis machine

Daily home hemodialysis (HD) patients have a much superior survival rate than patients on regular, 3 times a week in-center HD or on peritoneal dialysis. Present-day HD machines are unsuitable for use at home by patients. We present our concept of the ideal home HD machine that allows daily short and long HD, does all the work preparing for and cleaning up after dialysis, has an intravenous infusion system controlled by the patient, needs no systemic anticoagulation, and teaches and interacts with the patient during dialysis. To fulfill these functionalities, the dialyzer and blood tubing must be integrated with the machine and replaced less often than monthly, the machine must be capable of at least 200 L/week of hemodiafiltration, prepare all fluids necessary between and during dialyses, and all the components and fluids must be much beyond ultrapure

Severe Hypokalemia Induced by Hemodialysis

• During dialysis, it is assumed that the serum electrolyte levels asymptotically approach the concentration in the dialysate. In five patients, we observed an average 20% fall in serum potassium level, although the dialysate contained 42% more potassium than the predialysis serum. One patient had quadriplegia and near respiratory arrest as a complication of hypokalemia. The cause of the hypokalemia was a rapid shift of potassium from the extracellular to the intracellular space secondary to correction of acidosis. All patients entered dialysis with a history suggesting prolonged potassium loss, marked acidosis, and moderate hypokalemia; thus, the dialysate potassium concentration should be higher than normal, and frequent determinations of the serum potassium level should be performed. Therapy resulting in rapid correction of acidosis in uremic patients undergoing hemodialysis may cause large transcompartmental shifts of potassium. Potassium transfer across the dialysis membrane may be inadequate to compensate for such shifts, and life-threatening hypokalemia may occur. (Arch Intern Med 141:167-170, 1981