Solid Constituents Research Articles

Effects of substituting sweet potato flour for ground corn on performance, feeding behavior, and metabolism of dairy cows.

The objective of this study was to evaluate the effect of substituting sweet potato flour for ground corn in rations fed to lactating dairy on milk yield and composition, blood metabolites, and feeding behavior. Twenty lactating Holstein cows from 30 to 60days postpartum were randomly assigned to one of two groups (n = 10 each) and used in a cross-over design trial with two treatments: a standard concentrate with ground corn as an energy source or experimental concentrate with sweet potato flour (SPF) replacing all of the ground corn. Each of the 35-day periods consisted of 14days for adaptation to diet and 21days for data and sample collection. Milk yield, dry matter intake (DMI), and feeding behavior were evaluated daily throughout the trial. Milk samples were collected weekly and blood samples were collected every 3days. Milk was analyzed for fat, protein, lactose, and total solid constituents. Blood was analyzed for glucose, non-esterified fatty acid (NEFA), gamma-glutamyl transferase (GGT), aspartate aminotransferase (AST), total protein (TP), albumin, and urea concentrations. Milk yield (P = 0.62) and composition (fat: P = 0.71; protein: P = 0.12; lactose: P = 0.82; total solids: P = 0.56) were not affected by dietary treatments. There were no differences between treatments in DMI or meal frequency, but total eating time (P = 0.001), feeding time (P = 0.001), and meal duration (P = 0.001) was higher for control compared with SPF. However, feeding rate (P = 0.001) and serum urea concentration (P = 0.001) were higher for SPF compared with control. No differences were observed in serum metabolites and enzymes measured among treatments. The results of this trial indicate that SPF can be substituted for ground corn without impairing the performance, feeding behavior, and metabolism in dairy cows.

AN ANALYTICAL SOLUTION OF THE SATURATED AND INCOMPRESSIBLE POROELASTIC MODEL FOR TRANSIENT WAVE PROPAGATION

A transient wave propagation model is provided as a consequence of a new theory of porous media and wave propagation in saturated poroelastic media. This theory, in the linear case, becomes to be equivalent to the theory proposed by de Boer, R., Ehlers, W. & Liu, Z. in 1993. It leads to a model for the 1-D porous saturated column problem, which after the appropriate establishment of boundary and initial conditions, can be solved analytically with the aid of the Laplace transform concerning time. Numerical experiments are performed to illustrate the behavior of constituents displacement fields. The theory results in having an inertial effect on the motion of solid constituents as commonly expected. However, in contrast to Biot’s theory, is not introduced by the present theory the relative acceleration as an interactive force between solid and fluid constituents to account for the apparent inertial effect.

Evolution of Meniscal Biomechanical Properties with Growth: An Experimental and Numerical Study.

The menisci of the knee are complex fibro-cartilaginous tissues that play important roles in load bearing, shock absorption, joint lubrication, and stabilization. The objective of this study was to evaluate the interaction between the different meniscal tissue components (i.e., the solid matrix constituents and the fluid phase) and the mechanical response according to the developmental stage of the tissue. Menisci derived from partially and fully developed pigs were analyzed. We carried out biochemical analyses to quantify glycosaminoglycan (GAG) and DNA content according to the developmental stage. These values were related to tissue mechanical properties that were measured in vitro by performing compression and tension tests on meniscal specimens. Both compression and tension protocols consisted of multi-ramp stress–relaxation tests comprised of increasing strains followed by stress–relaxation to equilibrium. To better understand the mechanical response to different directions of mechanical stimulus and to relate it to the tissue structural composition and development, we performed numerical simulations that implemented different constitutive models (poro-elasticity, viscoelasticity, transversal isotropy, or combinations of the above) using the commercial software COMSOL Multiphysics. The numerical models also allowed us to determine several mechanical parameters that cannot be directly measured by experimental tests. The results of our investigation showed that the meniscus is a non-linear, anisotropic, non-homogeneous material: mechanical parameters increase with strain, depend on the direction of load, and vary among regions (anterior, central, and posterior). Preliminary numerical results showed the predominant role of the different tissue components depending on the mechanical stimulus. The outcomes of biochemical analyses related to mechanical properties confirmed the findings of the numerical models, suggesting a specific response of meniscal cells to the regional mechanical stimuli in the knee joint. During maturation, the increase in compressive moduli could be explained by cell differentiation from fibroblasts to metabolically active chondrocytes, as indicated by the found increase in GAG/DNA ratio. The changes of tensile mechanical response during development could be related to collagen II accumulation during growth. This study provides new information on the changes of tissue structural components during maturation and the relationship between tissue composition and mechanical response.

Finite Element Implementation of Biphasic-Fluid Structure Interactions in febio.

In biomechanics, solid-fluid mixtures have commonly been used to model the response of hydrated biological tissues. In cartilage mechanics, this type of mixture, where the fluid and solid constituents are both assumed to be intrinsically incompressible, is often called a biphasic material. Various physiological processes involve the interaction of a viscous fluid with a porous-hydrated tissue, as encountered in synovial joint lubrication, cardiovascular mechanics, and respiratory mechanics. The objective of this study was to implement a finite element solver in the open-source software febio that models dynamic interactions between a viscous fluid and a biphasic domain, accommodating finite deformations of both domains as well as fluid exchanges between them. For compatibility with our recent implementation of solvers for computational fluid dynamics (CFD) and fluid-structure interactions (FSI), where the fluid is slightly compressible, this study employs a novel hybrid biphasic formulation where the porous skeleton is intrinsically incompressible but the fluid is also slightly compressible. The resulting biphasic-FSI (BFSI) implementation is verified against published analytical and numerical benchmark problems, as well as novel analytical solutions derived for the purposes of this study. An illustration of this BFSI solver is presented for two-dimensional (2D) airflow through a simulated face mask under five cycles of breathing, showing that masks significantly reduce air dispersion compared to the no-mask control analysis. In addition, we model three-dimensional (3D) blood flow in a bifurcated carotid artery assuming porous arterial walls and verify that mass is conserved across all fluid-permeable boundaries. The successful formulation and implementation of this BFSI solver offers enhanced multiphysics modeling capabilities that are accessible via an open-source software platform.

The Composition of Intestinal Microbiota From Collichthys lucidus and Its Interaction With Microbiota From Waters Along the Pearl River Estuary in China

By their nature and geographical location, estuaries shape different marine habitats via freshwater and seawater interactions. Thus, fish intestinal microbiota, as mediated by estuary habitat fluctuations, are fundamentally important but rarely studied. Similarly, it is unclear how, and to what extent, water microbiota influences fish intestinal microbiota in different estuary habitats. In this study, the euryhaline fish species, Collichthys lucidus from three different habitats in the Pearl River estuary (PRE) was investigated to determine the influence of habitat fluctuation on intestinal microbiota. The three water environments selected for sample collection were very different, particularly for chlorophyll-a, suspended solid, and nutrient constituents. Using high-throughput sequencing of 16S rRNA gene amplicons, we observed that dominant microbial genera in surrounding estuary waters or fish intestines were seldom shared. The most dominant genera in water samples were Candidatus Actinomarina and HIMB11, while Bifidobacterium, Stenotrophomonas, Escherichia-Shigella and Rhodopseudomonas were more abundant in fish intestines. Fish hosts can shape fish intestinal microbiota. However, microbial exchange was also found between fish intestines and water samples. The frequency of microbial exchange between fish intestines and water samples was increased from upstream to downstream estuary points, and was influenced by changes in seawater salinity in the estuary. Finally, core intestinal microbiota from C. lucidus was analyzed, and showed that Bifidobacterium, Rhodopseudomonas, Escherichia-Shigella, Acinetobacter, and Stenotrophomonas were highly abundant. These microbiota were theoretically implicated in immune responses, nutrient metabolism, probiotics, and potential pathogen behaviors. Overall, these data highlighted the composition of C. lucidus intestinal microbiota in different habitats across the PRE.

Difference between breast milk jaundice and breast-feeding jaundice: literature review

Evidence shows that the different etiologies of neonatal jaundice, including breastfeeding and breast milk jaundice, have many different aspects. Therefore, the present study aims to conduct a literature review to compare breastfeeding and breast milk jaundice, ehich will furtherly help physicians and healthcare practitioners to have adequate information to properly establish an accurate diagnosis. The precise cause of breast milk jaundice is unclear. The majority of the suggested etiologies include factors found in human breast milk. Other theories point to possible genetic defects in the infected neonates. It has been reported that pregnane-3a,20ß-diol, epidermal growth factor, interleukin (IL)1ß, alpha-fetoprotein, and ß-glucuronidase are several factors that are solid constituents of the breast milk which may attribute to the development of this jaundice. Reports showed that breast milk jaundice usually develops in 20-30% of U.S. neonates, and most of whom are breastfed. Moreover, studies showed that more than one-third of infants on breastfeeding will eventually have high serum bilirubin levels that are ≥5 mg/dl. Evidence showed that the diagnosis should be considered when the levels of serum bilirubin exceed 5 mg/dl. Breast milk jaundice will usually fade away with no interventions, and in some cases, phototherapy inauguration and breast milk discontinuation might be needed. In breastfeeding jaundice, serum bilirubin levels usually peak within the first five or six days of life due to wrong or inadequate breastfeeding practices, and the management should be done by correcting these habits, while phototherapy might be applied when the bilirubin levels exceed 18-20 mg/dl.

Clogging in subsurface wastewater infiltration beds: genesis, influencing factors, identification methods and remediation strategies.

Subsurface wastewater infiltration (SWI) is an environmentally friendly technology for the advanced treatment of domestic sewage. Clogging (including physical, chemical and biological clogging) of the porous medium not only directly reduces the hydraulic load (treatment efficiency), but also reduces the service life. Although clogging has become one of the key issues discussed in several reports, there are still several gaps in understanding, especially in its occurrence process and identification. SWI clogging causes, development process and solutions are different from those of constructed wetlands. This article quotes some reports on constructed wetlands to provide technical ideas and reference for revealing SWI clogging problems. Based on the analysis of the clogging genesis, this review gathers the main factors that affect the degree of clogging, and new methods for the identification of clogging conditions. Some preventive and unclogging measures/strategies are presented. Finally, it is suggested that to effectively alleviate the clogging phenomenon and extend the service life, priority should be given to the comprehensive analysis of wastewater quality and solid constituents accumulated in the pores. Then, the effectiveness of in-situ strategies, such as alternating operation will be the main focuses of future research.

Collagen fibres determine the crack morphology in articular cartilage

Cracks in articular cartilage compromise tissue integrity and mechanical properties and lead to chondral lesions if untreated. An understanding of the mechanics of cracked cartilage may help in the prevention of cartilage deterioration and the development of tissue-engineered substitutes. The degeneration of cartilage in the presence of cracks may depend on the ultrastructure and composition of the tissue, which changes with aging, disease and habitual loading. It is unknown if the structural and compositional differences between immature and mature cartilage affect the mechanics of cartilage cracks, possibly predisposing one to a greater risk of degeneration than the other. We used a fibre-reinforced poro-viscoelastic swelling material model that accounts for large deformations and tension-compression non-linearity, and the finite element method to investigate the role of cartilage structure and composition on crack morphology and tissue mechanics. We demonstrate that the crack morphology predicted by our theoretical model agrees well with the histo-morphometric images of young and mature cracked cartilages under indentation loading. We also determined that the crack morphology was primarily dependent on collagen fibre orientation which differs as a function of cartilage depth and tissue maturity. The arcade-like collagen fibre orientation, first discussed by Benninghoff in his classical 1925 paper, appears to be beneficial for slowing the progression of tissue cracks by ‘sealing’ the crack and partially preserving fluid pressure during loading. Preservation of the natural load distribution between solid and fluid constituents of cartilage may be a key factor in slowing or preventing the propagation of tissue cracks and associated tissue matrix damage. Statement of significanceCracks in articular cartilage can be detrimental to joint health if not treated, but it is not clear how they propagate and lead to tissue degradation. We used an advanced numerical model to determine the role of cartilage structure and composition on crack morphology under loading. Based on the structure and composition found in immature and mature cartilages, our model successfully predicts the crack morphology in these cartilages and determines that collagen fibre as the major determinant of crack morphology. The arcade-like Benninghoff collagen fibre orientation appears to be crucial in ‘sealing’ the tissue crack and preserves normal fluid-solid load distribution in cartilage. Inclusion of the arcade-like fibre orientation in tissue-engineered construct may help improve its integration within the host tissue.

What Was Released? Assessing the Physical Properties and Chemical Composition of Petroleum and Products of Burned Oil

The severity of oil spills depends on the quantity of material released and its physical and chemical properties. The total amount of petroleum spilled during the Deepwater Horizon incident and the relative fractions of the chemical compound classes of the Macondo oil were obtained by measurements, observations, and model calculations, with a significant amount of uncertainty. Because petroleum is an extremely complex mixture of many thousands or more of gaseous, liquid, and solid constituents, full elucidation of their compositions at the molecular level is impossible with presently available analytical techniques. This paper reviews published work on widely used analytical techniques and points out that scientists’ varying approaches to research questions and preferences for methods of analysis constitute a source of uncertainty. In addition, the focus is on two technical advancements developed over the last two decades, namely two-dimensional gas chromatography and Fourier transform ion cyclotron resonance mass spectrometry. Both were particularly valuable in the analysis of the spilled Macondo oil and its weathering products. Among the different processes of alteration of the original oil, only in situ oil burning is dealt with in this paper. This review reveals the paucity of data on this mitigation process and shows the need for more systematic coordination of methods in burned oil research studies.

Influence of microencapsulated Phase Change Materials (PCMs) on the properties of polymer modified cementitious repair mortar

Microencapsulated Phase Change Materials (PCMs) can be directly incorporated into mortars to enhance their thermal performance. In this study, the addition of a commercial microencapsulated PCM in a polymer modified cement mortar was investigated, aiming at the development of a thermally efficient repair composite that may be used, along with textile reinforcement, for the structural and energy retrofitting of existing building envelopes. The effect of incorporating this PCM into the reference mortar at percentages ranging from 5% to 20% by wt. of solid constituents was thoroughly evaluated by assessing the physico-mechanical and thermal properties of the hardened end-product. Emphasis was placed on specific operational characteristics associated with the intended use of the modified mortar, such as its stress-strain behavior and temperature regulating efficiency. The results show a substantial drop in the mechanical properties of the composite with PCM addition, as well as an increase in its porosity and deformation capacity. In terms of thermal performance, the microencapsulated PCM contributed towards the attenuation and time shifting of temperature peaks. At dosages ≤20% by wt., it was thus possible to obtain mortars with favorable thermal characteristics, without compromising their physico-mechanical behavior to a degree that would preclude repair/strengthening applications.

Lyapunov stability of competitive cells dynamics in tumor mechanobiology

Poromechanics plays a key role in modelling hard and soft tissue behaviours, by providing a thermodynamic framework in which chemo-mechanical mutual interactions among fluid and solid constituents can be consistently rooted, at different scale levels. In this context, how different biological species (including cells, extra-cellular components and chemical metabolites) interplay within complex environments is studied for characterizing the mechanobiology of tumor growth, governed by intratumoral residual stresses that initiate mechanotransductive processes deregulating normal tissue homeostasis and leading to tissue remodelling. Despite the coupling between tumor poroelasticity and interspecific competitive dynamics has recently highlighted how microscopic cells and environment interactions influence growth-associated stresses and tumor pathophysiology, the nonlinear interlacing among biochemical factors and mechanics somehow hindered the possibility of gaining qualitative insights into cells dynamics. Motivated by this, in the present work we recover the linear poroelasticity in order to benefit of a reduced complexity, so first deriving the well-known Lyapunov stability criterion from the thermodynamic dissipation principle and then analysing the stability of the mechanical competition among cells fighting for common space and resources during cancer growth and invasion. At the end, the linear poroelastic model enriched by interspecific dynamics is also exploited to show how growth anisotropy can alter the stress field in spherical tumor masses, by thus indirectly affecting cell mechano-sensing.Graphic

An immersed phase field fracture model for microporomechanics with Darcy–Stokes flow

This paper presents an immersed phase field model designed to predict the fracture-induced flow due to brittle fracture in vuggy porous media. Due to the multiscale nature of pores in the vuggy porous material, crack growth may connect previously isolated pores, which leads to flow conduits. This mechanism has important implications for many applications such as disposal of carbon dioxide and radioactive materials and hydraulic fracture and mining. To understand the detailed microporomechanics that causes the fracture-induced flow, we introduce a new phase field fracture framework where the phase field is not only used as an indicator function for damage of the solid skeleton but also used as an indicator of the pore space. By coupling the Stokes equation that governs the fluid transport in the voids, cavities, and cracks and Darcy’s flow in the deformable porous media, our proposed model enables us to capture the fluid–solid interaction of the pore fluid and solid constituents during crack growth. Numerical experiments are conducted to analyze how the presence of cavities affects the accuracy of predictions based on the homogenized effective medium during crack growth.

Development and Mechanical Testing of Porous-Lightweight Geopolymer Mortar

In this study, a novel porous geopolymer mortar (GP) was produced and tested experimentally. Industrial waste materials/by-products were used as constituents of the GP, along with dune sand. One sample was produced as a control sample for benchmarking. For the rest of the samples, 15%, 30%, and 45% by volume, the solid constituents were replaced with expanded polystyrene foam (EPS) beads. These mortar samples were heat cured to depolymerize the EPS to cause porosity inside the samples. Indoor experiments were conducted to evaluate the response of produced porous GP to high heat flux. The porous samples were able to reduce heat transmission across the opposite surfaces. Induced porosity resulted in a decrement in compressive strength from 77.2 MPa for the control sample to 15.8 MPa for 45% porous sample. However, the limit lies within the standards for partitioning walls in buildings and pavements in urban areas to absorb rainwater.

Review on Milk Yield, Composition, Quality and Microbial Contamination Dairy Cattle Milk in Ethiopia

Ethiopian milk production depends on mainly indigenous livestock genetic resources dominated by small holder farmers. The estimated numbers of indigenous milking cows in Ethiopia is about nine million and are in the hands of smallholder farmers and pastoralists under traditional contributions of the sector to the country’s gross domestic product and exports. Milk and milk products play an important role in human nutrition throughout the world. Milk is also highly perishable and can easily be adulterated whilst the quality of the milk is highly dependent on farm management. Sources of microbial contamination of milk like milking environment, cows udder, milker, milking equipments and water the most dominant factor for the quality of milk. To prevent or retard growth of bacteria in milk and to maintain its quality for domestic consumption or transportation to the processing plant cooling, boiling and pasteurization are important to control measures of microbial contamination in raw milk. Clot on boiling test is performed by boiling a small amount of milk in a spoon, test tube or any other suitable container. Chemical composition, particularly milk fat content is used as quality test. The solid constituents of milk make an important food item from both nutritional as well as processing point of view. Keywords:- contamination, composition handling, milk quality DOI: 10.7176/JBAH/10-19-02 Publication date: October 31 st 2020

Exploring a deep LSTM neural network to forecast daily PM2.5 concentration using meteorological parameters in Kathmandu Valley, Nepal

Fine particulate matter (PM2.5) is a complex air pollutant with numerous gaseous and solid constituents. PM2.5 possesses a significant hazard due to its ability to penetrate deep into the lungs, corrode the alveolar wall, and impair lung functions. Modeling the non-linear and dynamic time series of daily PM2.5 concentration remains a challenge. This study proposes a deep LSTM neural network to forecast accurate PM2.5 concentration in the Kathmandu valley. Correlation analysis illustrates that dew, minimum ambient temperature, maximum ambient temperature, and pressure are strongly correlated with PM2.5 concentration. Hence, five models are developed based on different input parameter combinations and are eventually evaluated to determine the best performing model. Model 2 with single-step prediction is the best performing deep LSTM model with RMSE of 13.04 μg/m3 and MAE of 10.81 μg/m3. The SARIMA model applied to the univariate PM2.5 data series illustrates the RMSE of 19.54 μg/m3 and MAE of 15.21 μg/m3 for the test data. Hence, the deep LSTM model with past PM2.5 data and dew as inputs is recommended to predict future PM2.5 concentration in the Kathmandu valley. The negative impact of PM2.5 concentration on public health can be minimized with efficient forecasting.

Load-bearing characteristic of methane hydrate within coarse-grained sediments – Insights from isotropic consolidation

Gas hydrate, as a solid pore constituent, can potentially share external load with sediment matrix, and critically impact geological evolution of its hosting sediments, well integration and sediment settlement during gas production depending on its contribution to support external loading. We aim to address the question of whether hydrate shares the load with the soil skeleton through isotropic consolidation experiments. Our results highlight the formation of methane hydrate does not affect the integrity of sediment skeletons if the effective stress previously applied on the skeleton remains constant, which indicates that methane hydrate would not actively support the load. Subsequent external load applied to the sediments after hydrate formation can be supported by hydrate. Secondly, hydrate as well as hydrate-bearing sediments exhibit creep behavior. As hydrate creeps, the load transfers to the sediment skeleton with time and hydrate gradually retreats from the status of load-bearing. When hydrate saturation is low and the coexisting pore fluid can percolate through sediments, the local deformation of hydrate due to sediment consolidation induces excess pore pressure, which dissipates by pushing out the pore fluid. When the coexisting pore fluid is enclosed in hydrate mass in high hydrate saturation environments, the dissipation of excess pore pressure relies on the viscous flow of hydrate. This pressure dissipation could last for millions of years according to analytical analysis based on Terzaghi's consolidation theory, during which hydrate cannot completely escape the status of load-bearing. These observations conclude that load-bearing is a dynamic status rather than a stagnant pore habit, countering conventional thinking that load-bearing joins grain-coating, cementing and pore-filling as a pore habit of gas hydrate.

A continuum framework for coupled solid deformation–fluid flow through anisotropic elastoplastic porous media

We present a continuum framework for coupled solid deformation–fluid flow in anisotropic elastoplastic porous media. A thermodynamic formulation of the coupled processes gives rise to an anisotropic Biot tensor that is a function of drained elastic tangent moduli tensor of the solid skeleton and the intrinsic bulk modulus of the solid constituent. Two effective stress measures emerge from the formulation, namely, σ′, which is energy-conjugate to the elastic strain, and σ′′, which is energy-conjugate to the plastic strain. For the special case of transverse isotropy that is commonly encountered in natural rocks, the Biot tensor can be expressed in terms of its normal and tangential components to the bedding plane, along with a microstructure tensor. Apart from its thermodynamic consistency, an advantage of this new formulation is that standard mixed finite element formulation can be employed to discretize the domain and solve initial boundary-value problems. We conduct plane strain simulations of coupled solid deformation–fluid flow in a transversely isotropic porous medium to demonstrate the impacts of material anisotropy, stress history, and the Biot tensor on the system response.

A multi-scale material model for the estimation of the transversely isotropic thermal conductivity tensor of fired clay bricks

Fired clay bricks are employed in increasingly demanding application domains, such as multi-storey buildings and façades allowing only minimal heat loss. The latter requirement is often met by the use of pore forming agents. Then, pore size and morphology, as well as the thermal conductivity of the solid constituents of fired clay, govern the material's overall thermal conductivity tensor. We here quantify corresponding structure–property relations in the framework of random homogenization theory, introducing ellipsoidal shape and orientation distributions of material phases (including pores) at three different organizational levels. The model is validated by experimental techniques, such as scanning thermal microscopy, micro-computed tomography, and scanning electron microscopy. A final sensitivity analysis reveals that four design parameters heavily contribute to the overall thermal conductivity of fired clay bricks; namely the thermal conductivity of the fired clay matrix as well as the porosity of each of the three organizational levels.

Flow of viscoplastic fluids containing hybrid nanoparticles: Extended Buongiorno’s model

This paper investigates numerically the flow of a temperature-dependent viscoplastic fluid containing hybrid Ag and MgO nanoparticles through a ventilated heated cavity. A new approach for modeling the hybrid nanoparticle migration is proposed. The proposed model, which is based on Buongiorno’s non-homogeneous model, takes into account the nanoparticles mass flux due to both Brownian and thermophoretic diffusion, for each solid constituent. This is done by adding a mass conservation equation for each nanoparticle type, considering no mass flux at the walls. The results reveal that the nanoparticle distribution is the same for both constituents due to the dominance of inertia and buoyancy forces over slip mechanisms.

(Invited) Towards Addressing Fundamental Manufacturing Questions for Polymer Electrolyte Fuel Cell Electrodes

As a result of the expansion of material handling, backup power, and now, automotive markets for low-temperature fuel cells, the need to understand and overcome challenges to high-volume electrode production has never been greater. OEMs and system integrators globally are addressing these challenges specific to their systems and materials. However, fundamental questions remain to be answered, to the benefit of the entire industry. The interactions between the supported catalyst, ionomer, and dispersing media in the electrode ink, the method of dispersion of the solid constituents of the ink, and the interaction of the ink with the substrate, strongly impact the morphology and ultimately performance of the electrode. The ink formulation must also be appropriate for the coating and drying processes, the physics and parameters of which also impact electrode morphology and performance. Research efforts to address these questions are complicated by multiple pathways to construct the membrane electrode assembly (MEA) – including decal-transfer, catalyst-coated membrane, and gas-diffusion electrode structures – as well as a great variety of coating processes that could be used. These different structures not only potentially affect the performance of the MEA – and differently under different operating conditions – but they affect cost. In this talk, manufacturing pathways and challenges for electrodes will be discussed, and an overview of activities at the National Renewable Energy Laboratory to address these fundamental questions will be given.