Studies on Nitrogen and Silicon Deficiency in Microalgal Lipid Production

Microalgae are a rich, largely untapped source of lipids. Algae are underutilized, in part, because lipid formation generally is stimulated by stress, such as nutrient deficiency. Nutrient deficiencies reduce growth, resulting in a tradeoff between elevated cellular lipids and abundant cell division. This tradeoff is not well understood. We also have a poor understanding of the physiological drivers for this lipid formation. Here we report on three sets of research: 1) Assessment of species differences in growth and lipid content tradeoffs with high and low level nitrogen deficiency; 2) Investigation of physiological drivers of lipid formation, by mass balance accounting of cellular nitrogen with progressing deficiency; 3) Examination of the effects of sodium chloride and silicon on lipid production in a marine diatom. 1) Nitrogen deficiency typically had disproportionate effects on growth and lipid content, with profound differences among species. Optimally balancing the tradeoff required a wide range in the rate of nitrogen supply to species. Some species grew first and then accumulated lipids, while other species grew and accumulated lipids concurrently--a characteristic that increased lipid productivity. High lipid content generally resulted from a response to minimal stress. 2) Commonalities among species in cellular nitrogen at the initiation of lipid accumulation provided insight into the physiological drivers for lipid accumulation in nitrogen deficient algae. Total nitrogen uptake and retention differed widely among species, but the ratio of minimum retained nitrogen to nitrogen at the initiation of lipid accumulation was consistent among species at 0.5 ± 0.04. This suggests that lipid accumulation was signaled by a common magnitude of nitrogen deficiency. Among the cellular pools of nitrogen at the initiation of lipid accumulation, the concentration of RNA and the protein to RNA ratio were most similar among species with averages of 3.2 ± 0.26 g L-1 (8.2% variation) and 16 ± 1.5 (9.2% variation), respectively. This implicates critical levels of these parameters as potential signals initiating the accumulation of lipids. 3) In a marine diatom, low levels of either sodium chloride or silicon resulted in at least 50% increases in lipid content. The synergy of simultaneous, moderate sodium chloride and silicon stress resulted in lipid content up to 73%. There was a strong sodium chloride/silicon interaction in total and ash-free dry mass densities that arose because low sodium chloride was inhibitory to growth, but the inhibition was overcome with excessive silicon supply. This suggests that low sodium chloride may have affected metabolism of silicon

Increasing the Efficiency of a Surface Ionization Mass Spectrometer

An Avco surface ionization mass spectrometer (model 90,000) was installed at the Los Alamos Scientific Laboratory in February, 1968. Since that date this machine has been used as a production instrument for the isotopic analysis of uranium and plutonium samples. During 1969, it was realized that a problem inherent in the ionization mechanism of the instrument was degrading the accuracy of results, and that the number of man-hours expended in reducing data had become excessive. As soon as this situation became apparent, corrective action was initiated to reduce the effect of the ionization problem and to decrease the amount of people-time required for data reduction. A relatively sophisticated computer program called SPECTRE was written which has improved the accuracy of published results, and which has released two people from the tedious labor of hand data reduction. This paper describes the steps leading to the successful conclusion of this effort, and analyzes the completed computer program in some detail

Using double-sampling techniques to reduce the number of measurement trees during forest inventories

Variable-radius sampling techniques are commonly used during forest inventories. For each sample tree at a particular sampling point, diameter and height(s) are measured and then weight is estimated using established equations.  Heights can require a fair amount of time to measure in the field.  Separating the weight per acre estimate into two components; average basal area per acre and WBAR (individual tree weight-basal area ratio) across all points, can often lead to more efficient sampling schemes. Variable-radius sampling allows for a quick estimate of basal area per acre at a point since no individual tree measurements are needed.  If there is a strong relationship between weight and basal area, then by knowing basal area you essentially know weight.  Separation into two components is advantageous because in most cases there is more variability among basal area estimates per point then there is in WBAR. Hence, you can spend more resources establishing many points that only estimate basal area – often called “Count†points. “Full†points are those where individual tree measurements are also conducted. There is little published information quantifying the impacts on basal area, weight, etc., estimates among different “Full/Count†sample size ratios at the same site. Inventories were examined to determine this method’s applicability to loblolly pine plantations in southern Arkansas and northern Louisiana. Results show there is more variability among basal area estimates than WBAR and that the amount of trees being “intensively†measured is excessive.  Based on these four plantations, a “Full†point could be installed ranging from every other point to every fifth point depending on site conditions and the desired variable

Wave Motions In Molecular Clouds: Results in Two Dimensions

We study the linear evolution of small perturbations in self-gravitating fluid systems in two spatial dimensions; we consider both cylindrical and cartesian (i.e., slab) geometries. The treatment is general, but the application is to molecular clouds. We consider a class of equations of state which heuristically take into account the presence of turbulence; in particular, we consider equations of state which are {\it softer} than isothermal. We take the unperturbed cloud configuration to be in hydrostatic equilibrium. We find a class of wave solutions which propagate along a pressure supported cylinder (or slab) and have finite (trapped) spatial distributions in the direction perpendicular to the direction of propagation. Our results indicate that the dispersion relations for these two dimensional waves have similar forms for the two geometries considered here. Both cases possess a regime of instability and a fastest growing mode. We also find the (perpendicular) form of the perturbations for a wide range of wavelengths. Finally, we discuss the implications of our results for star formation and molecular clouds. The mass scales set by instabilities in both molecular cloud filaments and sheets are generally much larger than the masses of stars. However, these instabilities can determine the length scales for the initial conditions for protostellar collapse.Comment: 24 pages + 10 figures; self-extracting, uuencoded, compressed tarfil

Understanding precision nitrogen stress to optimize the growth and lipid content tradeoff in oleaginous green microalgae

Nitrogen deficiency promotes lipid formation in many microalgae, but also limits growth and lipid productivity. In spite of numerous studies, there is poor understanding of the interactions of growth and lipid content, the time course of lipid accumulation and the magnitude of nitrogen deficiency required to stimulate lipid formation. These relationships were investigated in six species of oleaginous green algae, comparing high and low levels of deficiency. Nitrogen stress typically had disproportionate effects on growth and lipid content, with profound differences among species. Optimally balancing the tradeoffs required a wide range in nitrogen supply rate among species. Some species grew first and then accumulated lipids, while other species grew and accumulated lipids concurrently which resulted in increased lipid productivity. Accumulation of high lipid content generally resulted from a response to minimal stress. The data highlight the tremendous biodiversity that may be exploited to optimally produce lipids with precision nitrogen stress

Comparing Economic Returns of Red Pine Plantation Thinning Scenarios Using Forest Vegetation Simulator (FVS)

Red pine (Pinus resinosa Ait) plantations are an important cover type of Department of Natural Resources (DNR) lands because of relatively high yields and economic value. Out of the approximate 400,000 acres of Minnesota red pine plantations one-fifth of the acreage is managed by the DNR. The DNR recently established a policy to rescind purposeful management to manage all red pine plantations to extended rotation ages, or rotation ages beyond those maximizing economic returns or biological yields. With recent state budget issues, DNR management is under greater scrutiny by the public, particularly on School Trust lands. Hence, most red pine plantations are now going to be managed on economic rotation ages (both School Trust and Non-trust lands). The objective of this study was to use a growth and yield model system to help determine the optimal number of thinnings, residual stand density following thinnings, and final harvest rotation age to maximize economic returns. Stumpage revenues received by the DNR from fiscal years 2011 to 2014 were used, allowing for a sensitivity analysis of the optimum thinning scenario since four distinct sets of stumpage revenues were compared. For simplicity, it was assumed that all harvested timber was red pine. Five different thinning treatments and an unthinned scenario were examined. Thinning scenarios differed as to the timing of thinnings based on standing basal area per acre and the residual basal area per acre following the thinning. A final harvest was implemented, the timing differing among the scenarios based on when financial returns were maximized. The greatest economic return appears to occur when light, but frequent thinnings occur. A target basal area of 150 square feet leaving 120 square feet was optimum (150_120) for all four sets of revenues. Optimum final harvest rotation ages varied from 60 to 70 years depending on the stumpage revenues. A thinning scenario of a target 150 square feet leaving 90 square feet (150_90) was nearly financially optimum and would likely allow for more operationally realistic thinning regimes

Healthcare Barriers of Residents at a Subsidized Housing Community

Introduction: Despite expanded healthcare programs, the low income and elderly lack coverage of vision, hearing, and dental services. Community services are often asked to fill these gaps. To evaluate the situation in Burlington, VT, we surveyed staff and residents in Burlington Housing Authority (BHA) subsidized housing to (1) identify gaps in healthcare coverage and (2) assess barriers to accessing those services in this population.https://scholarworks.uvm.edu/comphp_gallery/1207/thumbnail.jp