The Elmer E. Rasmuson Library Occasional Papers, no.12

The preparation, publication, and distribution of this guide was made possible by a special appropriation from the Alaska State Legislature in 1981.Preface -- Biographical outline of Maurice Robert "Mike" Gravel -- Introduction -- Scope and content note -- Collection outline of the Mike Gravel Papers, 1957-1980 -- Series descriptions -- About the microfich

Verification of the whitetopping thickness design procedure for asphalt concrete overlaid Portland cement concrete pavements

Iowa is one of few states with a large number of Portland Cement Concrete (PCC) pavements. Many of these pavements have been rehabilitated by placing multiple layers of Asphalt Concrete (AC) over the existing PCC slabs. However, there was a need for an alternative with a longer life and lower life-cycle cost. With improvements in paving technology such as the slipform paver and the ability to obtain high early age strength, PCC overlays soon became that alternative. Many of the existing overlay design procedures were developed for a single placed layer of pavement and are not applicable to the two layered AC/PCC pavements. Previous research developed a method so that the single placed layer concept can be applied to the analysis and design of overlays for AC/PCC pavements. The study presented here is an extension of this research. It investigates existing design methodologies and presents modifications for future research

Stabilization of localized structures by inhomogeneous injection in Kerr resonators

We consider the formation of temporal localized structures or Kerr comb generation in a microresonator with inhomogeneities. We show that the introduction of even a small inhomogeneity in the injected beam widens the stability region of localized solutions. The homoclinic snaking bifurcation associated with the formation of localized structures and clusters of them with decaying oscillatory tails is constructed. Furthermore, the inhomogeneity allows not only to control the position of localized solutions, but strongly affects their stability domains. In particular, a new stability domain of a single peak localized structure appears outside of the region of multistability between multiple peaks of localized states. We identify a regime of larger detuning, where localized structures do not exhibit a snaking behavior. In this regime, the effect of inhomogeneities on localized solutions is far more complex: they can act either attracting or repelling. We identify the pitchfork bifurcation responsible for this transition. Finally, we use a potential well approach to determine the force exerted by the inhomogeneity and summarize with a full analysis of the parameter regime where localized structures and therefore Kerr comb generation exist and analyze how this regime changes in the presence of an inhomogeneity

Investigation of LED Light Qualities for Peppermint (Mentha x Piperita L.) Cultivation Focusing on Plant Quality and Consumer Safety Aspects

To understand how peppermint responds to different LED light qualities during the early vegetative phase, peppermints were illuminated with three different LED light conditions (RB = Red/Blue, RGB = Red/Green/Blue, SUN = artificial sunlight closely resembling the terrestrial sunlight spectrum between 380 and 780 nm) in an automated vertical cultivation system. RB resulted in compact growth, whereas both green-containing lighting conditions induced excessive stem and side branch elongations and significant leaf expansions. Although peppermint plants achieved marketable appearances regardless of lighting condition, essential oil (EO) compositions with highly elevated amounts of pulegone and menthofuran did not meet consumer safety requirements. Both artificial SUN and RB spectra showed lower concentrations of pulegone in the EO at 41 and 43%, respectively, than detected under RGB at more than 49%. Reasons for this undesirable EO composition are discussed as a result of the lighting conditions applied and the early harvest time, leading to an incomplete reduction of pulegone to menthone during biosynthesis. Based on these findings, aromatic peppermint cultivation under LEDs can be improved to meet regulatory requirements and highlights the need for analytical quality controls regarding consumer safety to evaluate the applicability of LED lighting for fresh herb productions

Facing energy limitations – approaches to increase basil (Ocimum basilicum L.) growth and quality by different increasing light intensities emitted by a broadband LED light spectrum (400-780 nm)

Based on the current trend towards broad-bandwidth LED light spectra for basil productions in multi-tiered controlled-environment horticulture, a recently developed white broad-bandwidth LED light spectrum (400-780 nm) including far-red wavelengths with elevated red and blue light fractions was employed to cultivate basil. Four Ocimum basilicum L. cultivars (cv. Anise, cv. Cinnamon, cv. Dark Opal and cv. Thai Magic) were exposed to two different rising light intensity conditions (ILow and IHigh). In dependence of the individual cultivar-specific plant height increase over time, basil cultivars were exposed to light intensities increasing from ~ 100 to ~ 200 µmol m-2 s-1 under ILow, and from 200 to 400 µmol m-2 s-1 under IHigh (due to the exponential light intensity increases with decreasing proximity to the LED light fixtures). Within the first experiment, basils’ morphological developments, biomass yields and time to marketability under both light conditions were investigated and the energy consumptions were determined to calculate the basils’ light use efficiencies. In detail, cultivar-dependent differences in plant height, leaf and branch pair developments over time are described. In comparison to the ILow light conditions, IHigh resulted in accelerated developments and greater yields of all basil cultivars and expedited their marketability by 3-5 days. However, exposure to light intensities above ~ 300 µmol m-2 s-1 induced light avoidance responses in the green-leafed basil cultivars cv. Anise, cv. Cinnamon and cv. Thai Magic. In contrast, ILow resulted in consumer-preferred visual qualities and greater biomass efficiencies of the green-leafed basil cultivars and are discussed as a result of their ability to adapt well to low light conditions. Contrarily to the green-leafed cultivars, purple-leafed cv. Dark Opal developed insufficiently under ILow, but remained light-tolerant under IHigh, which is related to its high anthocyanin contents. In a second experiment, cultivars’ volatile organic compound (VOC) contents and compositions over time were investigated. While VOC contents per gram of leaf dry matter gradually decreased in purple-leafed cv. Dark Opal between seedling stage to marketability, their contents gradually increased in the green cultivars. Regardless of the light treatment applied, cultivar-specific VOC compositions changed tremendously in a developmental stage-dependent manner

Empirical essays in labor economics

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Stationary localized structures and the effect of the delayed feedback in the Brusselator model

The Brusselator reaction-diffusion model is a paradigm for the understanding of dissipative structures in systems out of equilibrium. In the first part of this paper, we investigate the formation of stationary localized structures in the Brusselator model. By using numerical continuation methods in two spatial dimensions, we establish a bifurcation diagram showing the emergence of localized spots. We characterize the transition from a single spot to an extended pattern in the form of squares. In the second part, we incorporate delayed feedback control and show that delayed feedback can induce a spontaneous motion of both localized and periodic dissipative structures. We characterize this motion by estimating the threshold and the velocity of the moving dissipative structures.Comment: 18 pages, 11 figure