Browsing by Subject "Algae"
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Item Algae biofuels in Texas(2009-08) Salpekar, Ashwini; Sylvie, George; Malcolm Brown Jr., RobertTexas – the energy center of the world – is emerging as a pioneer in algae biodiesel research and production. There are a number of reasons for this. Texas is the largest emitter of CO₂ in the country, and efforts are being made to reduce the state's dependence on fossil fuels. Also, algae – robust and promising organisms – need non-arable land, lots of sunlight and brackish/waste water, along with CO₂. Texas has all of these in abundance, plus universities and algae start-ups that are doing crucial RItem Application of Hedonic Price Modeling to Estimate the Value of Algae Meal(2012-10-19) Gogichaishvili, IliaHigh productivity rates, usage of nonproductive land, renewability and recovery of waste nutrients and potential for CO2 emission reduction represent some of the advantages that selected algae species might have over competing products. Many research studies have investigated potential usage of algae for different purposes, such as cosmetics or aquaculture; however most of the research studies have focused on the feasibility of algae as a source of second generation biodiesel and feed meal. Because of its high costs of production, using algae only for the purpose of biodiesel production might not be profitable. Thus, for global scale algae commercialization it is important that it be used as a feed meal along with being marketed to the biodiesel industry. One of the major problems faced by economists when attempting to analyze the feasibility of algae is the absence of a market for algae-based fuel and meal. Given that no market exists, prices for algae cannot be observed and realistic investment analysis becomes difficult to perform in this sector. The objective of this study is to estimate a potential price of algae meal using hedonic pricing techniques. For that purpose, twenty two different feed meals commonly having the same usage as Post Extracted Algae Residue (PEAR) are decomposed into their chemical constituents in order to calculate the market value of each characteristic. Calculated prices of these characteristics are then used to estimate the price of algae meal and compare it to different feed meals. Results suggest that algae prices are strictly variable to its chemical components across different algae types. Besides, PEAR represents a sustainable source of financial value and might be considered one of the cornerstones in making algae commercialization a feasible and profitable option.Item Characterizing Microalgae (Nannochloris oculata) Harvesting by Aluminum Flocculation(2012-02-14) Davis, Ryan T.Recent progress in algae biotechnology indicates that microalgae have the potential of becoming a significant source for food, feed proteins, nutraceuticals, and lipids for biofuels. Typically low concentrations of microalgae cultures (less than 2 g/L) make harvesting of algae biomass one of the key economic bottlenecks for microalgae production of biofuels and bioproducts. Among the various biomass harvesting options currently under consideration, flocculation appears to be the least expensive and most flexible method for harvesting and initial concentration of dilute algal cultures. In addition to initial biomass concentration, processing factors that could also affect harvesting efficiency include culture pH, flocculant dosage, and media ionic strength (conductivity). This thesis reviews challenges of harvesting and concentration of green microalgae and examines the effect of pH, flocculant dosage, and culture conductivity on charge neutralization and flocculation of Nannochloris oculata by aluminum chloride. N. oculata flocculation was studied by manipulating the culture pH and ionic strength before the addition of aluminum chloride. The removal efficiency, concentration factor, settling rate, and zeta potential of the culture were measured to assess the effect of processing variables and understand mechanisms that govern N. oculata flocculation by aluminum chloride. Flocculation tests conducted with culture concentrations of 10^7 cells/ml revealed that AlCl3 concentration of 0.05 g/L and flocculation pH of 5.3 were optimal conditions for achieving 100% removal efficiency and a twentyfold algae concentration. At flocculant concentrations greater than 0.05 g/L, removal efficiencies were equally good but resulting concentration factors decreased with increasing AlCl3 dosage. Zeta potential measurements were correlated with flocculation dosage, initial cell concentration, medium pH, and aluminum solubility curves to conclude that densely charged multi-valent aluminum hydroxide species were responsible for the efficient flocculation at pH 5.3 with 0.05 g/L AlCl3.Item Constraints on algal biofuel production(2011-05) Beal, Colin McCartney; Ruoff, Rodney S.; Webber, Michael E., 1971-; Hebner, R. E. (Robert E.); Berberoglu, Halil; Seibert, A F.; King, Carey W.The aspiration for producing algal biofuel is motivated by the desire to replace conventional petroleum fuels, produce fuels domestically, and reduce greenhouse gas emissions. Although, in theory, algae have the potential to produce a large amount of petroleum fuel substitutes and capture carbon emissions, in practice, profitable algal biofuel production has proven quite challenging. This dissertation characterizes the production pathways for producing petroleum fuel substitutes from algae and evaluates constraints on algal biofuel production. Chapter 8 provides a summary of the entire dissertation. The first chapter provides a framework for reporting the production of renewable diesel from algae in a consistent way by using data that are specific and by presenting information with relevant metrics. The second chapter presents a review of analytical tools (i.e., microscopy, spectroscopy, and chromatography) that can be used to analyze the structure and composition of intermediate products in an algal biofuel production pathway. In chapters 3 through 6, the energy return on investment, water intensity, and financial return on investment are presented for three cases: 1) an Experimental Case in which data were measured during five batches of algal biocrude production with a combined processed volume of about 7600 L, 2) a hypothetical Reduced Case that assumes the same energy output as the Experimental Case, with reduced energy and material inputs, and 3) a Highly Productive Case that assumes higher energy outputs than the Experimental Case, with reduced energy and material inputs, similar to the Reduced Case. For all three cases, the second-order energy return on investment was determined to be significantly less than 1, which means that all three cases are energy negative. The water intensity (consumption and withdrawal) for all cases was determined to be much greater than that of conventional petroleum fuels and biofuels produced from non-irrigated crops. The financial return on investment was also found to be significantly less than 1 for all cases, indicating production would be unprofitable. Additionally, it was determined that large-scale algal biofuel production would be constrained by the availability of critical energy and material inputs (e.g., nitrogen and carbon dioxide). The final part of this dissertation presents a first-principles thermodynamic analysis that represents an initial attempt at characterizing the thermodynamic limits for algal biofuel production. In that analysis, the energy, entropy, and exergy is calculated for each intermediate product in the algal biofuel production pathway considered here. Based on the results presented in this body of work, game-changing technology and biotechnology developments are needed for sustainable and profitable algal biofuel production.Item Coupling algae biofilm cultivation with wastewater treatment for sustainable biomass production and nutrient recycling(2015-05) Campbell, Daniel Martin; Berberoglu, Halil; Murphy, ThomasThe main objective of this study was to model the transport phenomena through which algal biofilms are able to recover nutrients contained within secondarily treated wastewater and to gauge the potential of hydrothermal liquefaction process water as a viable nutrient source. The cultivation of algae in the form of biofilms has shown promise due to this technique's greater energy return on investment during cultivation. These biofilms are known to be nutrient transport limited, thus an understanding of the phenomena associated with nutrient transport into algal biofilms is necessary for the optimized design and effective implementation of fixed cultivation techniques. This thesis reports a numerical study that investigates the transport of dissolved nutrients from wastewater into biofilms and an experimental study of the suitability of hydrothermal liquefaction process water as a nutrient source for algal cultivation. For the numerical study, the biofilm is modeled as a flat surface whose composition and growth characteristics were obtained from values in the literature. The fluid over the biofilm is modeled as a one-dimensional flow over a flat surface. The transport of dissolved nutrients was assumed to be diffusion dominated into the biofilm and was described through Fick's law. A novel derivation of the concentration boundary layer was demonstrated for use in a fully developed, thin fluid layer. The areal algal productivity and the nutrient removal rate by the biofilm were determined using the generated model and were validated against the literature data. The results showed that biofilm productivity and nutrient removal rates are highly sensitive to the presence of boundary layers, with a nearly order of magnitude decrease in productivity within the first meter of the modeled reactor. Finally, a parametric study on the effects of fluid velocity and depth on nutrient removal rates was performed. The study indicated the nutrient uptake rates increased by 24% with a 50% reduction in fluid depth and increased by 118% with a ten-fold increase in fluid velocity In the second part of this thesis, nitrate and phosphate concentrations in the process water of hydrothermal liquefaction of municipal biosolids were determined by ion chromatography to gauge its potential as a nutrient medium for algal cultivation. A parametric study on the effect of process conditions with the intent of determining the best nutrient source for algal cultivation indicated that the aqueous nutrient content was largely unaffected by heating rate, but was highly sensitive to the type of biosolid.Item Development of a novel algae biofilm photobioreactor for biofuel production(2012-08) Ozkan, Altan; Berberoglu, Halil; Kinney, Kerry; Katz, Lynn; Kirisits, Mary J.; Lawler, Desmond; Brand, Jerry; Cetiner, SelimAlgae are photosynthetic microorganisms that convert carbon dioxide and sunlight into biomass that can be used for biofuel production. Although they are usually cultivated in suspension, these microorganisms are capable of forming productive biofilms over substrata given the right conditions. This dissertation focuses on algal biofilms and their application in biofuel feedstock production. In particular it reports the construction and performance of an algae biofilm photobioreactor, the physico-chemical surface properties of different algal species and adhesion substrata, and cell-surface interactions based on experimental results and theoretical models. A novel algae biofilm photobioreactor was constructed and operated (i) to demonstrate the proof of concept, (ii) to analyze the performance of the system, and (iii) to determine the key advantages and short comings for further research. The results indicated that significant reductions in water and energy requirements were possible with the biofilm photobioreactor. Although the system achieved net energy ratio of about 6, the overall productivity was low as Botryococcus branunii is notoriously slow growing algae. Thus, further studies were focused on identification of algal species capable of biofilm growth with larger biomass and lipid productivities. Adhesion of cells to substrata precedes the formation of all biofilms. A comprehensive study has been conducted to determine the interactions of a planktonic and a benthic algal species with hydrophilic and hydrophobic substrata. The physico-chemical surface properties of the algal cells and substrata were determined and using these data, cell-substrata interactions were modeled with the thermodynamic, Derjaguin, Landau Verwey, Overbeek (DLVO) and Extended Derjaguin, Landau, Verwey, Overbeek (XDLVO) approaches and critical parameters for algal adhesion were identified. Finally, the adhesion rate and strength of algal species were quantified with parallel plate flow chamber experiments. The results indicated that both cell and substrata surface hydrophobicity played a critical role for the adhesion rate and strength of the cells and XDLVO approach was the most accurate model. Finally, based on these findings the physico-chemical surface properties of ten algal species and six substrata were quantified and a screening was done to determine algae species substratum couples favoring adhesion and biofilm formation.Item Genetic basis for ichthyotoxicity and osmoregulation in the euryhaline haptophyte, Prymnesium parvum N. Carter(2014-05) Talarski, Aimee Elizabeth; La Claire, John W., 1951-There is limited information currently available regarding the underlying physiological responses and molecular mechanisms of osmoregulation, acetate metabolism [in relation to the synthesis of glycerolipids, polyunsaturated fatty acids (PUFA), and ichthyotoxins], and transport in Prymnesium parvum N. Carter, a microalga that causes devastating harmful algal blooms (HAB) worldwide. This dissertation examines gene expression under environmental conditions that are associated with HAB formation, including phosphate limitation and low salinity, using microarrays and RNA sequencing (RNA-Seq). A comparative fatty acid methyl ester (FAME) analysis at 30 vs. 5 practical salinity units (psu) was performed to gain additional insight into acetate metabolism. The RNA-Seq analysis included a de novo assembly of the P. parvum transcriptome, generating 47,289 transcripts, of which 35.4% were identifiable. This permitted the evaluation of the expression of many more genes compared with the microarray analysis, which examined ~3,500 genes. Relevant candidate genes identified included those whose products are involved in osmolyte production, salinity stress, and ion transport. With respect to the putative synthesis of polyketide ichthyotoxins, 32 different polyketide synthase (PKS) transcripts were identified in the transcriptome assembly, none of which were differentially expressed. Hemolysin and monogalactosyldiacylglycerol synthase were downregulated at 30 vs. 5 psu, suggesting the increased presence of additional ichthyotoxins at the lower salinity. Evidence for several PUFA synthesis pathways was also revealed. Fatty acid compositions were largely similar at the two salinities, containing relatively prominent quantities of the PUFA stearidonic acid, but compositions varied among strains. The transcription of genes whose products are associated with vesicular transport was elevated, and higher levels of extracellular prymnesins were observed in HAB-forming conditions. Thus, with regard to acetate metabolism, I have revealed evidence for the post-transcriptional regulation of the production of prymnesins and the contributory effects of hemolysin, monogalactosyldiacylglycerol, and PUFA towards ichthyotoxicity. Further, I propose that toxin transport is triggered in HAB-forming conditions, in which the toxins are actively being excreted. Collectively, these data shed light on the transcriptional responses that occur following alterations in phosphate availability and salinity, including those associated with the synthesis and delivery of a number of potential ichthyotoxins from P. parvum.Item Growth Rate of Marine Microalgal Species using Sodium Bicarbonate for Biofuels(2013-08-05) Gore, MatthewWith additional research on species characteristics and continued work towards cost effective production methods, algae are viewed as a possible alternative biofuel crop to current feedstocks such as corn. Current open pond production methods involve bubbling carbon dioxide (CO_(2)) gas into the media to provide a carbon source for photosynthesis, but this can be very inefficient releasing most CO_(2) back into the atmosphere. This research began by investigating the effect of sodium bicarbonate (NaHCO_(3)) in the growth media as an alternative carbon source to bubbling CO_(2) into the cultures. The second part examined if NaHCO_(3) could act as a lipid trigger in higher (10.0 g/L) concentrations. The microalgae species Dunaliella tertiolecta (Chlorophyta), Mayamaea spp. (Baciallariophyta) and Synechoccocus sp. (Cyanophyta) were grown with 0.0 g/L, 0.5g/L, 1.0 g/L, 2.0 g/L and 5.0 g/L dissolved NaHCO_(3) in modified seawater (f/2) media. To investigate effects of NaHCO_(3) on lipid accumulation, growth media cultures were divided into two ?lipid phase? medias containing either 0.0g/L (non-boosted) or 10.0 g/L (boosted) NaHCO_(3) treatments. Culture densities were determined using spectrophotometry, which showed both all three species are able to successfully grow in media ameliorated with these high NaHCO_(3) concentrations. Highest growth phase culture densities occurred in NaHCO_(3) concentrations of 2.0 g/L for D. tertiolecta and Mayamaea spp., and the 5.0 g/L treatment for Synechoccocus sp. Highest growth rates occurred in the 5.0 g/L NaHCO_(3) concentration treatments for D. tertiolecta, Mayamaea spp., and Synechoccocus sp. (0.205 d-1 ?0.010, 0.119 d-1 ?0.004, and 0.372 d-1 ?0.003 respectively). As a lipid accumulation trigger two of the three species (D. tertiolecta and Mayamaea spp) had their highest end day oil indices in a 10.0 g/L treatment. Highest oil indices occurred in boosted 5.0 g/L Dunaliella tertiolecta and 2.0 g/L Mayamaea spp. (13136 ? 895 and 62844 ? 8080 respectively (relative units)). The results obtained indicate NaHCO3 could be used as a photosynthetic carbon source for growth in all three species and a lipid trigger for D. tertiolecta and Mayamaea spp.Item An integrated resource and biological growth model for estimating algal biomass production with geographic resolution(2010-12) Wogan, David Michael; Da Silva, Alexandre K., 1975-; Webber, Michael E., 1971-This thesis describes a geographically- and temporally-resolved, integrated biological and engineering model that estimates algal biomass and lipid production under resource-limited conditions with hourly and county resolution. Four primary resources are considered in this model: sunlight, carbon dioxide, water, and land. The variation in quantity and distribution of these resources affects algae growth, and is integrated into the analysis using a Monod model of algae growth, solar insolation data, and published values for water, carbon dioxide, and land availability. Finally, lipid production is calculated by assuming oil content based on dry weight of the biomass. The model accommodates a range of growth and production scenarios, including water recycling, co-location with wastewater treatment plants and coal-fired generators, and photobioreactor type (open pond or tubular), among others. Results for every county in Texas indicate that between 86 million and 2.2 billion gallons of lipids per year can be produced statewide for the various growth scenarios. The analysis suggests that algal biomass and lipid production does indeed vary geographically and temporally across Texas. Overall, most counties are water-limited for algae production, not sunlight or carbon dioxide-limited. However, there are many nuances in biomass and lipid production by county. Counties in west Texas are typically not solar- or land-limited, but are constrained by either water or carbon dioxide resources. Consequently, counties in east Texas are limited by either water, or land (depending on the fraction of water recycling). Varying carbon dioxide concentration results in higher growth rates, but not always increased biomass and lipid production because of limitations of other resources in each county.Item Polymer applications for improved biofuel production from algae(2011-12) Jones, Jessica Naomi; Poenie, Martin F.; Brand, Jerry; Brodbelt, Jennifer; Georgiou, George; Roy, Krishnendu; Seibert, FrankBiofuel is a renewable and sustainable energy source with near-neutral carbon footprint. Algae are an ideal feedstock for biofuel production because they reproduce quickly and have high oil. Algae can be cultivated in non-arable land, and would not impact the food supply. Unfortunately, processing algae into biofuel is more expensive than land crops due to the large volumes of dilute algal suspension that must be harvested and concentrated. In order to improve algae-based biofuel economics, resins were developed that reduce costs associated with water pumping and transport. Hydrophobic resins were developed for binding oil out of an algal suspension so that the residual biomass could be recovered without solvent contamination. Binding behavior displayed lipid species specificity, and binding capacity was improved by ethanol treatment of the biomass. Algae was harvested by binding to anion exchange resin and directly converted into biodiesel. One-step, room temperature in situ transesterification of algae yielded nearly as much biodiesel as two-step, heated transesterification of dried biomass. Elution with transesterification reagent also regenerated the resin for subsequent algal binding. Functionalized resins were developed with high algal binding capacity at neutral pH. Binding was easily reversed, as treatment with buffer with pH higher than pKa of the resin functional group removed the algae and regenerated the resin for subsequent use. The resin bound 10% of its weight in algae and released it as a 100-fold concentrated suspension. The polymers developed can be scaled up for commercial processes and reduce algal harvesting and concentration costs.Item Radiant and thermal energy transport in planktonic and benthic algae systems for sustainable biofuel production(2011-05) Murphy, Thomas Eugene; Berberoglu, Halil; Howell, John R.Biofuel production from microalgal biomass offers a clean and sustainable liquid fuel alternative to fossil fuels. In addition, algae cultivation is advantageous over traditional biofuel feedstocks as (i) it does not compete with food production, (ii) it potentially has a much greater areal productivity, (iii) it does not require arable land, and (iv) it can use marginal sources of water not suitable for irrigation or drinking. However, current algae cultivation technologies suffer from (i) low solar energy conversion effiencies, (ii) large thermal fluctuations which negatively affect the productivity, and (iii) large evaporative losses which make the process highly water intensive. This thesis reports a numerical study that address these key issues of planktonic as well as benthic algal photobioreactor technologies. First, radiant energy transfer in planktonic algal photobioreactors containing cells with different levels of pigmentation was studied. Chlamydomonas reinhardtii and its truncated chlorophyll antenna transformant tla1 were used as model organisms. Based on these simulations guidelines are derived for scaling the size and microorganism concentration of photobioreactors cultivating cells with different levels of pigmentation to achieve maximum photosynthetic productivity. To achieve this, the local irradiance obtained from the solution of the radiative transport equation (RTE) was coupled with the specific photosynthetic rates of the microorganisms to predict both the local and total photosynthetic rates in a photobioreactor. For irradiances less than 50 W/m2, the use of genetically modified strains with reduced pigmentation was shown to have negligible effect on increasing photobioreactor productivity. However, at irradiances up to 1000 W/m2, improvements of up to 30% were possible with cells having 63% less pigment concentration. It was determined that the ability of tla1 to transmit light deeper into the photobioreactor was the primary mechanism by which a photobioreactor using the modified strain can achieve greater productivity. Furthermore, it was determined photobioreactors using each strain have dead zones in which the local photosynthetic rate is negligible due to nearly complete light attenuation. These dead zones occur at local optical thicknesses greater than 169 and 275 in photobioreactors using the wild strain and the genetically modified strain, respectively. In addition, a thermal model of an algae biofilm photobioreactor was developed to assess the thermal fluctuations and evaporative loss rate of these novel photobioreactors under varying outdoor conditions. The model took into account air temperature, irradiance, relative humidity, and wind speed as inputs and computed the temperature and evaporative loss rate as a function of time and location in the photobioreactor. The model was run for a week-long period in each season using weather data from Memphis, TN. The range of the daily algae temperature variation was observed to be 13.2C, 12.4C, 12.8C, and 9.4C in the spring, summer, winter, and fall, respectively. Furthermore, without active cooling, the characteristic evaporative water loss from the system is approximately 6.3 L/m2-day, 7.0 L/m2-day, 4.9 L/m2-day, and 1.5 L/m2-day in the spring, summer, fall, and winter, respectively.Item Rheology of algae slurries(2010-12) Bolhouse, Angel Michele; Berberoglu, Halil; Ferron, RaissaThis thesis reports the rheological properties of algae slurries as a function of cell concentration for three microalgae species: Nannochloris sp.,Chlorella vulgaris, and Phaeodactylum tricornutum. Rheological properties ofalgae slurries have a direct impact on the agitation and pumping power requirements as well as process design for producing algal biofuels. This study measures the rheological properties of eight diff erent concentrations of each species ranging from 0.5 to 80 kg dry biomass/m³. Strain-controlled steady rate sweep tests were performed for each sample with an ARES-TA rheometer using a double wall couette cup and bob attachment. Shear rates ranged from 5 - 270 s⁻¹, corresponding to typical expected conditions. The results showed that Nannochloris sp. slurry behaved as a Newtonian fluid for concentrations up to 20 kg/m³. Samples with concentrations above 40 kg/m³ behaved as a shear thinning non-Newtonian fluid. The effective viscosity increased with increased biomass concentration for a maximum value of 3.3x10⁻³ Pa-s. Similarly, C. vulgaris slurry behaved as a Newtonian fluid with concentrations of up to 40 kg/m³, above which it displayed a shear thinning non-Newtonianf behavior and a maximum eff ective viscosity of 3.5x10⁻² Pa-s. On the other hand, P. tricornutum slurry demonstrated solely Newtonian fluid behavior, with the dynamic viscosity increasing with increasing biomass concentration for a maximum value of 3.2x10⁻³ Pa-s. The maximum observed e ffective viscosity occurred at a concentration of 80 kg/m³ for all three species. Moreover, an energy analysis was performed where a non-dimensional bioenergy transport e ffectiveness was de termined as the ratio of the energy content of the transported algae biomass to the sum of the required pumping power and the harvesting power. The results show that the increase in major losses due to increase in viscosity was overcompensated by the increase in the transported biomass energy. Also, cultivating a more concentrated slurry requires less dewatering power and is the preferred option. The largest bioenergy transport eff ectiveness was observed for the slurries with the largest initial dry biomass concentrations. Finally, the relative viscosity of algae slurries was modeled using a Kelvin-Voit based model for dilute and concentrated viscoelastic par- ticle suspensions. The model, which depends primarily on the packing factor of the algae species, agrees with the measured viscosity with an average error of 18%, while the concentrated particle suspension model was slightly more accurate than the dilute suspension model.Item Studies of phylogenetic relationships and evolution of functional traits in diatoms(2014-05) Nakov, Teofil; Theriot, Edward C. (Edward Claiborne), 1953-The research presented here deals with inferring phylogenetic trees and their use to study the evolution of functional traits in diatoms (Heterokontophyta: Bacillariophyceae). Two chapters are concerned with the phylogeny of a mainly freshwater group, the Cymbellales, with a convoluted taxonomic history and classification. I generated a multi-gene dataset to test the monophyly of the Cymbellales and reconstruct the relationships within the order. The molecular data were equivocal with respect to the monophyly of the Cymbellales, especially when taking into account some problematic taxa like Cocconeis and Rhoicosphenia. Aside from the problem with their monophyly, my work shows that the current genus- and family-level classification of the Cymbellales is unnatural, arguing for the need of nearly wholesale re-classification of the group. The two following chapters make use of phylogenetic trees to model the evolution of functional traits. I explored the evolution of cell size across the salinity gradient finding that the opposing selective forces exerted by marine and fresh waters select for different optimal cell sizes -- larger in the oceans and smaller in lakes and rivers. Thereafter, I modelled the evolutionary histories of habitat preference (planktonic-benthic) and growth form (solitary-colonial) across the diatoms. These traits exhibit markedly different evolutionary histories. Habitat preference evolves slowly, is conserved at the level of large clades, and its evolution is generally uniform across the tree. Growth form, on the other hand, has a more dynamic evolutionary history with frequent transitions between the solitary and colonial growth forms and rates of evolution that vary through time. I hope that these empirical studies represent an incremental advancement to the understanding of the evolution diatom species and functional diversity.