Electrostatic subframing and compressive-sensing video in transmission electron microscopy.

We present kilohertz-scale video capture rates in a transmission electron microscope, using a camera normally limited to hertz-scale acquisition. An electrostatic deflector rasters a discrete array of images over a large camera, decoupling the acquisition time per subframe from the camera readout time. Total-variation regularization allows features in overlapping subframes to be correctly placed in each frame. Moreover, the system can be operated in a compressive-sensing video mode, whereby the deflections are performed in a known pseudorandom sequence. Compressive sensing in effect performs data compression before the readout, such that the video resulting from the reconstruction can have substantially more total pixels than that were read from the camera. This allows, for example, 100 frames of video to be encoded and reconstructed using only 15 captured subframes in a single camera exposure. We demonstrate experimental tests including laser-driven melting/dewetting, sintering, and grain coarsening of nanostructured gold, with reconstructed video rates up to 10 kHz. The results exemplify the power of the technique by showing that it can be used to study the fundamentally different temporal behavior for the three different physical processes. Both sintering and coarsening exhibited self-limiting behavior, whereby the process essentially stopped even while the heating laser continued to strike the material. We attribute this to changes in laser absorption and to processes inherent to thin-film coarsening. In contrast, the dewetting proceeded at a relatively uniform rate after an initial incubation time consistent with the establishment of a steady-state temperature profile.

Survey of need for industrial hygienists.

Grass roots surveys of the need for industrial hygienists, areas of specialization, and related subjects can fill a real void in currently available information. AIHA local sections and other professional groups may wish to conduct regional studies similar to the one described here. A pooling of results by reporting to their national organizations would be beneficial to all in the profession.

The management of severe preeclampsia and eclampsia with intravenous diazoxide.

Twelve patients with either severe preeclampsia (9) or eclampsia (3) were treated with intravenous diazoxide, 300-mg bolus, for the reduction of diastolic blood pressure (less than or equal 110 torr) after the usual and customary measures had been initiated to include parenteral MgSO4 and diazepam. Diazoxide precipitously decreased both systolic and diastolic blood pressure proportionately (35-50%); the nadir was invariably reached in 5-15 minutes. Diastolic pressure never fell below 50 torr, and mean arterial pressure always exceeded 70 torr. Oliguria was not apparent. The vasodepressor response was fairly persistent for 4 hours in all but 3 patients; 2 of these received a second 300-mg dose. Significant changes in fetal heart activity (bradycardia, dysrhythmia) were observed in only 1 patient. Labor was immediately ablated in all patients, but could be restimulated with oxytocin. All pregnancies were terminated within 7 hours (mean, 3.7 hours), seven of them by cesarean section. Eleven newborns did well. We conclude that the immediate reduction in maternal arterial blood pressure is without apparent hazard to the mother as well as the fetus.