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

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

The dynamics of a ringing church bell

Church bell ringing as practised in the UK involves large-amplitude motions of both bell and clapper. A simulation model is developed and validated against experimental measurements. It is shown that the clapper does not hit the bell with a single impact but a long series of bounces, and this has important consequences for the decay profile of the bell vibration. Information relevant to bell-ringers and bell-hangers is collected in a series of design charts derived from the simulation model. These charts can assist in the diagnosis and correction of faults. Arising from the analysis of the bouncing clapper, a more general result is also presented relating to the frequency bandwidth when any structure is excited by a small bouncing impactor, for example an impulse hammer used in vibration testing.Peer Reviewe

Genomics: Think Global, Act Local

Long a slogan for environmentalists, “think global, act local” could be a new rallying cry for biologists. As genome-wide techniques advance and their costs drop, scientists are expanding into larger and larger territories—metagenomics, global proteomic approaches, and analyses of thousands of genomes. These massive data sets are opening up new possibilities for understanding some of the smallest details of the genome. Here, we look at four such cases—investigating the evolutionary role of insertions and deletions in the genome, connecting an orphan enzyme with its gene, mapping the fine details of chromatin structure, and characterizing global interactions between proteins and RNA—all of which depend on a combination of global thinking and local action

A Multi-Center, Qualitative Assessment of Pediatrician and Maternal Perspectives on Rotavirus Vaccines and the Detection of Porcine circovirus

<p>Abstract</p> <p>Background</p> <p>In 2010, researchers using novel laboratory techniques found that US-licensed rotavirus vaccines contain DNA or DNA fragments from <it>Porcine circovirus </it>(PCV), a virus common among pigs but not believed to cause illness in humans. We sought to understand pediatricians' and mothers' perspectives on this finding.</p> <p>Methods</p> <p>We conducted three iterations of focus groups for pediatricians and non-vaccine hesitant mothers in Seattle, WA, Cincinnati, OH, and Rochester, NY. Focus groups explored perceptions of rotavirus disease, rotavirus vaccination, and attitudes about the detection of PCV material in rotavirus vaccines.</p> <p>Results</p> <p>Pediatricians understood firsthand the success of rotavirus vaccines in preventing severe acute gastroenteritis among infants and young children. They measured this benefit against the theoretical risk of DNA material from PCV in rotavirus vaccines, determining overall that the PCV finding was of no clinical significance. Particularly influential was the realization that the large, randomized clinical trials that found both vaccines to be highly effective and safe were conducted with DNA material from PCV already in the vaccines.</p> <p>Most mothers supported the ideal of full disclosure regarding vaccination risks and benefits. However, with a scientific topic of this complexity, simplified information regarding PCV material in rotavirus vaccines seemed frightening and suspicious, and detailed information was frequently overwhelming. Mothers often remarked that if they did not understand a medical or technical topic regarding their child's health, they relied on their pediatrician's guidance.</p> <p>Many mothers and pediatricians were also concerned that persons who abstain from pork consumption for religious or personal reasons may have unsubstantiated fears of the PCV finding.</p> <p>Conclusions</p> <p>Pediatricians considered the detection of DNA material from PCV in rotavirus vaccines a "non-issue" and reported little hesitation in continuing to recommend the vaccines. Mothers desired transparency, but ultimately trusted their pediatrician's recommendation. Both vaccines are currently approved for their intended use, and no risk of human PCV illness has been reported. Communicating this topic to pediatricians and mothers requires sensitivity to a broad range of technical understanding and personal concerns.</p

Factors associated with testicular self-examination among unaffected men from multiple-case testicular cancer families

<p>Abstract</p> <p>Background</p> <p>The lifetime testicular cancer (TC) risk in the general population is relatively low (~1 in 250), but men with a family history of TC are at 4 to 9 times greater risk than those without. Some health and professional organizations recommend consideration of testicular self-examination (TSE) for certain high-risk groups (e.g. men with a family history of TC). Yet little is known about factors associated with TSE behaviors in this at-risk group.</p> <p>Methods</p> <p>We collected information on this subject during an on-going NCI multidisciplinary, etiologically-focused, cross-sectional Familial Testicular Cancer (FTC) study. We present the first report specifically targeting TSE behaviors among first- and second-degree relatives (n = 99) of affected men from families with ≥ 2 TC cases. Demographic, medical, knowledge, health belief, and psychological factors consistent with the Health Belief Model (HBM) were evaluated as variables related to TSE behavior, using chi-square tests of association for categorical variables, and t-tests for continuous variables.</p> <p>Results</p> <p>For men in our sample, 46% (n = 46) reported performing TSE regularly and 51% (n = 50) reported not regularly performing TSE. Factors associated (p < .05) with regularly performing TSE in multivariate analysis were physician recommendation and testicular cancer worry. This is the first study to examine TSE in unaffected men from FTC families.</p> <p>Conclusion</p> <p>The findings suggest that, even in this high-risk setting, TSE practices are sub-optimal. Our data provide a basis for further exploring psychosocial issues that are specific to men with a family history of TC, and formulating intervention strategies aimed at improving adherence to TSE guidelines.</p