Spectral Dependence of Rise Time in Gas Filled Phototubes: Implications concerning Possible Miniaturization of Gas Discharge Detectors of Electromagnetic Radiation

The rise time of a gas-filled photodiode at blue-green wavelengths is found to be less than that at red wavelengths. As photoionization of excited atoms in such devices increases response to light of decreasing wavelength over that provided by the photocathode, spectral differences in rise time are also attributed to the same mechanism. It is suggested that these phenomena decrease parasitic inductance of the tube. This implies that rise times in glow discharge detectors of EM radiation can be improved through miniaturization of inter-electrode spacing.     

Glow Discharge Detection of Long Wavelength Electromagnetic Radiation: Cascade Ionization Process Internal Signal Gain and Temporal and Spectral Response Properties

The mechanism of long wave electromagnetic signal detection by glow-discharge plasma, based upon gas breakdown theory by high frequency electric fields, is developed to include internal signal amplification of the order of that associated with the photomultiplier, upper and lower limits to response linearity, temporal and spectral response properties, and noise in the abnormal glow discharge. Agreement between signal-to-noise expressions in this analysis and measurements involving simple and inexpensive glow discharge indicator lamps exhibiting excellent sensitivity to microwave radiaion is quite good. An inherent ideal limit to speed of response is derived which indicates picosecond-order risetimes are theoretically possible if parasitic reactance effects which limit risetimes of present day devices to microsecond order can be overcome. Sensitivity can be improved further by increasing the number of free electrons. Enhanced diffusion current losses for a subnormal glow yield spectrally flat response which can be useful in radiometric applications.     

Restoration of images degraded by extreme mechanical vibrations

A method of numerically calculating the optical transfer function appropriate to any type of image motion and vibration, including random, has been recently developed. This method has been verified experimentally with real vibrations, and the close agreement justifies implementation in image restoration from blur deriving from any type of image motion, including random displacement. Here, image restorations of actual physically degraded images are presented, based on a constrained least squares improvement of the original Wiener filter. Even for extreme vibrations where the blur extent is much larger than the blurred detail, restoration is quite complete. The key to restoration is the determination of the optical transfer function unique to the particular image motion and vibration causing the blur. Results are also presented for low vibration frequency motion of random blur extent, as well as for high vibration frequencies.     

The Effective Cross Section

The effection cross section concept for low intensity light illumination of gas discharges is shown to be analogous to high intensity breakdown of gases as interpreted by Panarella's "effective photon" concept. This mathematical result is suggested as a possible interpretation of strikingly similar nonlinearities of gas breakdown by light measured in both cases at their respectively different intensity levels.     

Zebrafish embryos (Danio rerio) using microinjection

Low membrane permeability is one of the major obstacles to the successful cryopreservation of zebrafish embryos. The aim of the present study was to explore if this could be overcome by yolk modification with different cryoprotectants by micro-injection. Initial investigation of two cryoprotectants, methanol and sucrose, was undertaken to determine their suitability for micro-injection supplementation of the yolk mass. Intact zebrafish embryos at 50% epiboly stage were injected with Hanks' solution, 5.2 M methanol or 1.3 M sucrose yielding approximate final concentrations of 2.0 and 0.5 M of the cryoprotectants within the yolk sac respectively. After micro-manipulation, the embryos were cultured at 28 degree C for three days and their survival assessed at the hatching stage. All micro-manipulations performed in the present study resulted in a significant decrease in embryo survival (P < 0.05). Embryos micro-injected with methanol or sucrose were also subjected to a cooling procedure. They were placed in 3M methanol + 0.5 M sucrose at room temperature for 30 min and then cooled from 20 degree C to 0 degree C at 2 degree/min, from 0 degree C to -7.5 degree/min at 1 degree/min, seeded at -7.5 degree C and held for 10 min, before cooling at 0.3 degree/min to - 20 degree C or until full crystallization in all embryos. The processes of extra- and intracellular crystallization were studied by cryomicroscopy. The temperature of intracellular crystallization did not differ significantly between control and injected embryos. However, it was found that intracellular crystallization did not always happen instantly after extracellular crystallization.     

Subnormal Glow Discharge Detection of Optical and Microwave Radiation

Commercial indicator lamp glow discharge tubes in the subnormal glow mode exhibit variable frequency tuned filter video response to optical and microwave radiation. Sensitivity to optical radiation can be particularly increased by using such devices in the subnormal rather than abnormal glow. These phenomena are discussed in terms of physical electronics and an equivalent circuit. A comparison is made of abnormal and subnormal glow mode properties. It is hoped that this model can lead to glow discharge lamp design for specific circuit applications involving subnormal glow mode characteristics. Relationships between glow discharge detector physical and electronic parameters are derived.     

Wind-Power Transforming Systems

In this article, we give a brief account of theoretical and experimental investigations, as well as engineering designs, of different types of rotors (propeller-type rotors and Darrieus-type rotors). In numerical studies, we used the vortex lattice method. We obtained instant and averaged-in-time values of the coefficients of the centrifugal, drag, side, and head forces, as well as the value of the relative torque, the wind-power use coefficient, the configuration of the vortex trace, and the velocity field and contour lines. The results of numerical studies agree well with experimental data.     

Relationship between the changes in cellular volume of fish spermatozoa and their cryoresistance

We have investigated the hypothesis that the spermatozoa of marine fish are more resistant than freshwater species to the dynamic changes in osmotic pressure that occur during the process of cryopreservation. We show that while the spermatozoa of marine fish can be successfully activated across a wide range of osmotic pressures (0-2000 mOsmol/l), those of the freshwater species only survive activation within a more restricted range (0-300 mOsm/l). After freeze-thawing, up to 30 percent of motile cells were found in silver carp samples, while up to 90 percent of motile cells were observed in samples from the haarder (Mugil soiuy B). Haarder spermatozoa showed no change of cell volume after dilution in activating or cryoprotective media, while the silver carp spermatozoa responded by swelling and eventual cell disruption. We propose that the differences in cryoresistance of silver carp (Hypophthalmichthys molitrix V.) and haarder spermatozoa may be determined by the ability to preserve cellular volume under non-isotonic conditions.