High speed shutter

A shutter element is described which is formed by a loop of an electrically conductive ribbon disposed adjacent to the end of a passageway to be shuttered. The shuttered end of the passageway is cut at an acute angle. The two leg portions of the ribbon loop are closely spaced to each other and disposed in a plane parallel to the axis of the passageway. A pulse of high current is switched through the loop to cause the current flowing in opposite directions through adjacent leg portions of the ribbon. This produces a magnetically induced pressure on one of the legs of the ribbon forcing the leg over the end of the passageway in gas tight sealing engagement, and thereby blocking passageway

Photomultiplier blanking circuit

Circuit for protecting photomultiplier equipment from current surges which occur when exposed to brilliant illumination is discussed. Components of circuit and details of operation are provided. Circuit diagram to show action of blanking pulse on zener diode is included

Photomultiplier circuit including means for rapidly reducing the sensitivity thereof

A simple, reliable and inexpensive control circuit is described for rapidly reducing the bias voltage across one or more of the dynode stages of a photomultiplier, to substantially decrease its sensitivity to incoming light at those times where excess light intensity might damage the tube. The control circuit comprises a switching device, such as a silicon controlled rectifier (SCR), coupled between a pair of the electrodes in the tube, preferably the cathode and first dynode, or the first and second dynodes, the switching device operating in response to a trigger pulse applied to its gate to short circuit the two electrodes. To insure the desired reduction in sensitivity, two switching stages, the devices be employed between two of the electrode stages, the devices being operated simultaneously to short circuit both stages

Optical shutter for use in shock tubes

Thin metal shutter that is forced into angled optical slit isolates spectrograph from high speed shock tube both optically and mechanically so neither radiation nor particulate material enters spectrograph

Calibration of radiation detectors in the ultraviolet region between 972 and 2500 A

The development of experimental setups and procedures is considered for calibrating photosensitive devices in the spectral range 1022 to 2500 A for which no direct calibration techniques exist. An indirect technique that uses a sodium salicylate detector calibrated outside this range was developed for use as a secondary standard. The primary standard was a xenon-filled ionization chamber, which is an absolute standard over the wavelength interval 972 to 1022 A. Measurements made by this method were checked at 1470 A with a xenon lamp and at 2537 A with a mercury arc lamp and a 0.5 m blaze monochromator with a grating blazed at 2000 A. The overall accuracy of the measurements was + or - 40 percent or better

Analysis of the Aboriculture Industry Safety Culture from the Standpoint of Injures, Illnesses, Employee Response, and Industry Standards

The author researched 215 recorded injuries and illnesses to all field employees between January 1, 1991 and July 1, 2002 at an arboricultural company in California. Detailed interviews were conducted with each of the 38 field employees to determine employee perceptions of safety training, management, communication, and personal discomfort to provide a clearer picture of the company safety program. This information was correlated with the tree worker claims and industry standards to determine the effectiveness of the safety program based on employee discomforts and claim related descriptive statistics. The claims\u27 tabulations show that back strains are the most prominent injuries in terms of lost days and total costs, but pruning has the greatest number of lost time injuries. Pruning involves equipment such as chainsaws, hand saws, and pole saws, which equate to 35% of the total lost time injuries and 38% of the total claims\u27 costs. More specifically, pruning equipment such as hand saws and pole saws, result in only 8% of total lost time injuries and only 10% of the total cost of claims. The arborist discomfort surveys revealed that elbow and shoulder pain are just as common as lower back pain. The body motion from the use of pole saws and pole primers are the direct cause of this pain and this is consistent with employee opinion. This repetitive strain disorder is becoming an epidemic among arborists and has not been adequately addressed by arborist trade organizations, the State of California, or the American National Standards Institute. Because the safety program is based on the ANSI Z133 Tree Care Operations standards and the California Code of Regulations: Tree Work, Maintenance or Removal, significant deficiencies in the program can be correlated with the inadequacies of the standards. Based on the information collected for this thesis, recommendations were made regarding company safety training, arborist work practices, mechanical assists, equipment design, and industry standards

Electrical stimulation of visual cortex can immediately improve spatial vision

Published in final edited form as:Curr Biol. 2016 July 25; 26(14): 1867–1872. doi:10.1016/j.cub.2016.05.019.SUMMARY We can improve human vision by correcting the optics of our lenses [1, 2, 3]. However, after the eye transduces the light, visual cortex has its own limitations that are challenging to correct [4]. Overcoming these limitations has typically involved innovative training regimes that improve vision across many days [5, 6]. In the present study, we wanted to determine whether it is possible to immediately improve the precision of spatial vision with noninvasive direct-current stimulation. Previous work suggested that visual processing could be modulated with such stimulation [7, 8, 9]. However, the short duration and variability of such effects made it seem unlikely that spatial vision could be improved for more than several minutes [7, 10]. Here we show that visual acuity in the parafoveal belt can be immediately improved by delivering noninvasive direct current to visual cortex. Twenty minutes of anodal stimulation improved subjects’ vernier acuity by approximately 15% and increased the amplitude of the earliest visually evoked potentials in lockstep with the behavioral effects. When we reversed the orientation of the electric field, we impaired resolution and reduced the amplitude of visually evoked potentials. Next, we found that anodal stimulation improved acuity enough to be measurable with the relatively coarse Snellen test and that subjects with the poorest acuity benefited the most from stimulation. Finally, we found that stimulation-induced acuity improvements were accompanied by changes in contrast sensitivity at high spatial frequencies.This work was supported by grants from the NIH (R01-EY019882, R01-EY025275, P30-EY08126, T32-EY007135, F31-MH102042). We thank the reviewers and Randolph Blake for helpful comments. We thank Kevin Dieter for technical assistance in designing the psychophysical procedure for experiment 5. Subjects gave informed written consent to procedures approved by the Vanderbilt University Institutional Review Board and were compensated at a rate of $10/hr for their time. (R01-EY019882 - NIH; R01-EY025275 - NIH; P30-EY08126 - NIH; T32-EY007135 - NIH; F31-MH102042 - NIH)Accepted manuscrip