Measurement of the spectral and spatial responses of the human eye\u27s blue sensitive system and the effects of lateral inhibition by the red and green sensitive systems

A study was conducted to measure the change in spatial modulation sensitivity of the human eye\u27s blue sensitive system at low light levels due to color shift, intensity change, and accommodation of red and green sensitive systems with yellow light. A testing device was designed which allowed a wide range of variation in viewing conditions for targets of several spatial frequencies. IV Results indicate that the ability to resolve gratings by the blue cones is depressed by lowering grating intensities but does not depend on wavelength within the blue cone sensitivity envelope to any extent greater than that explained by simple spectral sensitivity. Applying a uniform yellow illumination over the gratings, exciting red & green cone systems, depresses the ability to detect gratings consistent with Weber\u27s law. This implies no lateral inhibition between the blue cones and the red or green cones at low intensities

Preparation of malachite green leucocyanide and a study of the effects of dye impurities

Using a modification of a preparation method published by Tobin, Katzakian, and Chisholm, the photochromic leucocyanide of malachite green dye was prepared in a pure form. This leucocyanide was doped with various amounts of the dye as an impurity and the effect of the dye on the photolysis and fade reactions tested. It was determined that the dye has the effect of merely masking the leucocyanide during photolysis exposure but does chemically increase the completeness of the fade reaction

Development of ionic liquid multi-mode spacecraft micropropulsion systems

This dissertation presents work on development of multi-mode specific spacecraft propulsion systems. Specifically, this work attempts to realize a single propellant capable of both chemical monopropellant and electric electrospray rocket propulsion, develop methods to characterize multi-mode propulsion system performance, and realize a system capable of both monopropellant and electrospray propulsion for a small spacecraft. Selection criteria for ionic liquid propellants capable of both monopropellant and electrospray propulsion are developed. These are based on desired physical properties and performance considering use in both propulsive modes. From these insights, a monopropellant mixture of 1-ethyl-3-methylimidazolium ethyl sulfate and hydroxylammonium nitrate is selected and synthesized. Multi-mode spacecraft micropropulsion systems which include a high-thrust chemical mode and high-specific impulse electric mode are assessed. Due to the combination of a common propellant for both propulsive modes, low inert mass, and high electric thrust, the monopropellant/electrospray system has the highest mission capability in terms of delta-V for missions lasting shorter than 150 days. The ionic liquid monopropellant mixture is tested for decomposition on heated platinum, rhenium, and titanium surfaces. It was found that the propellant decomposes at 165 ⁰C on titanium, which is the decomposition temperature of HAN, and 85 ⁰C on platinum. Arrhenius-type reaction rate parameters were calculated from the results and used to develop thruster models. The [Emim] [EtSO4]-HAN propellant mixture is tested in a capillary electrospray emitter and exhibits stable electrospray emission at a nominal extraction voltage of 3400 V. The highest specific impulse attained in these experiments was 412 seconds; however, this could be improved with a more robust feed system design. This data, along with data from the monopropellant decomposition experiment is used to design a multi-mode micropropulsion system using a common propellant and common thruster geometry. This system is capable of ~20-40% greater delta-V capability at a given mission duration compared to a system utilizing separate, state-of-the-art monopropellant and electrospray thrusters --Abstract, page iv

Persistencies in the Labour Market

Using longitudinal income-tax registers, we study how past labour market outcomes affect current labour market transition rates. We focus on hysteresis effects of the durations and incidence of previous spells out of work. We estimate flexible multi-state Mixed Proportional Hazard specifications for transition rates between employment, unemployment, and welfare/non-participation. Our main finding is that after longer periods of employment with high income, individuals' transition rates from unemployment to employment increase. Longer periods of non-employment generally decrease future transition rates to work, and sometimes also from work. The quantitative magnitude of persistency and hysteresis effects on inequality is modest.duration analysis, hysteresis, inequality, wages, unemployment, hazard rates, employment, income, work

Summary statement of the Asilomar conference on recombinant DNA molecules

This meeting was organized to review scientific progress in research on recombinant DNA molecules and to discuss appropriate ways to deal with the potential biohazards of this work. Impressive scientific achievements have already been made in this field and these techniques have a remarkable potential for furthering our understanding of fundamental biochemical processes in pro- and eukaryotic cells. The use of recombinant DNA methodology promises to revolutionize the practice of molecular biology. Although there has as yet been no practical application of the new techniques, there is every reason to believe that they will have significant practical utility in the future

Surface effects in the crystallization process of elastic flexible polymers

Investigating thermodynamic properties of liquid-solid transitions of flexible homopolymers with elastic bonds by means of multicanonical Monte Carlo simulations, we find crystalline conformations that resemble ground-state structures of Lennard-Jones clusters. This allows us to set up a structural classification scheme for finite-length flexible polymers and their freezing mechanism in analogy to atomic cluster formation. Crystals of polymers with "magic length" turn out to be perfectly icosahedral