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Orthologous proteins contain sequence disparity guided by natural selection. In certain cases, species-specific protein functionality predicts pharmacological enhancement, such as greater specific activity or stability. However, immunological barriers generally preclude use of nonhuman proteins as therapeutics, and difficulty exists in the identification of individual sequence determinants among the overall sequence disparity. Ancestral sequence reconstruction (ASR) represents a platform for the prediction and resurrection of ancient gene and protein sequences. Recently, we demonstrated that ASR can be used as a platform to facilitate the identification of therapeutic protein variants with enhanced properties. Specifically, we identified coagulation factor VIII (FVIII) variants with improved specific activity, biosynthesis, stability, and resistance to anti-human FVIII antibody–based inhibition. In the current study, we resurrected a panel of ancient mammalian coagulation factor IX (FIX) variants with the goal of identifying improved pharmaceutical candidates. One variant (An96) demonstrated 12-fold greater FIX activity production than human FIX. Addition of the R338L Padua substitution further increased An96 activity, suggesting independent but additive mechanisms. after adeno-associated virus 2 (AAV2)/8-FIX gene therapy, 10-fold greater plasma FIX activity was observed in hemophilia B mice administered AAV2/8-An96–Padua as compared with AAV2/8-human FIX–Padua. Furthermore, phenotypic correction conferred by the ancestral variant was confirmed using a saphenous vein bleeding challenge and thromboelastography. Collectively, these findings validate the ASR drug discovery platform as well as identify an ancient FIX candidate for pharmaceutical development.

Ancestral sequence reconstruction provides a unique platform for investigating the molecular evolution of single gene products and recently has shown success in engineering advanced biological therapeutics. To date, the coevolution of proteins within complexes and protein–protein interactions is mostly investigated in silico via proteomics and/or within single-celled systems. Herein, ancestral sequence reconstruction is used to investigate the molecular evolution of 2 proteins linked not only by stabilizing association in circulation but also by their independent roles within the primary and secondary hemostatic systems of mammals. Using sequence analysis and biochemical characterization of recombinant ancestral von Willebrand factor (VWF) and coagulation factor VIII (FVIII), we investigated the evolution of the essential macromolecular FVIII/VWF complex. Our data support the hypothesis that these coagulation proteins coevolved throughout mammalian diversification, maintaining strong binding affinities while modulating independent and distinct hemostatic activities in diverse lineages.

The development of small molecules to stabilize the G-quadruplex structure has garnered significant attention for anticancer drug discovery. Herein, we report the synthesis of several 4,4'-diaminoazobenzene derivatives containing different substituent groups and their ability to bind and stabilize telomeric G-quadruplex DNA. Circular dichroism (CD) spectroscopy was performed to characterize the quadruplex topologies, measure stabilization effects, and evaluate their capabilities for conformational photoregulation. 4,4'-Diaminoazobenzene derivatives were found to moderately stabilize quadruplex structures but not affect conformational photoregulation. This work further develops the design and general understanding of the stabilization effects of small molecules with telomeric G-quadruplex DNA.

Nickelate (e.g. Pr2NiO4) exhibits high activity towards the oxygen reduction reaction over a wide temperature range (600 - 900 oC), which makes it a promising candidate as an advanced cathode for solid oxide fuel cells. However, a phase transition occurs in Pr2NiO4 during cell operation, following: Pr2NiO4 à Pr6O11 + Pr3Ni2O7. As a result, the quantification of the degree of phase transformation becomes necessary to understand the structure-electrochemical property relationship. In this presentation, we report our recent work on (1) replacing the oxide current collector with a gold metal grid, which enables the cathode to expose to the x-ray beam. The x-ray analysis was performed at room temperature and (2) utilizing in situ capability to study the kinetics and mechanisms of phase evolution and establishing the relationship between high-temperature structures and the electrochemical performance. Finally, we will compare the XRD results acquired from room temperature with these in situ studies. This material is based upon work supported by the U.S. Department of Energy under Award Number DE-FE0023475.

Biological rhythms in neuroendocrine and immune systems are pervasive. Daily and seasonal changes in day lengths regulate multiple physiological and immunological parameters in a diverse range of animals. A series of studies have shown that epigenetic modifications exhibit naturally occurring rhythms across short- and long-term timescales. In this chapter, we describe daily, estrous and seasonal oscillations in epigenetic enzymes in neuroendocrine substrates, peripheral reproductive tissues and immune cells (e.g. leukocytes). The predominant focus of the chapter includes enzymes involved in DNA methylation and histone modifications, such as DNA methyltransferase and histone deacetylases. The findings presented herein highlight that epigenetic modifications can be permanent as well as transient with long-term consequences on the timing of physiological and behavioural processes. Moreover, the bidirectional interaction between the immune system and the neuroendocrine nucleus that controls biological rhythmicity, the suprachiasmatic nucleus, emphasizes the need to understand rhythmic changes in epigenetic enzymes and the consequences of disrupted daily and seasonal rhythms.

BACKGROUND: Coagulation factor VIII represents one of the oldest protein-based therapeutics, serving as an effective hemophilia A treatment for half a century. Optimal treatment consists of repeated intravenous infusions of blood coagulation factor VIII (FVIII) per week for life. Despite overall treatment success, significant limitations remain including treatment invasiveness, duration, immunogenicity, and cost. These issues have inspired research into the development of bioengineered FVIII products and gene therapies. OBJECTIVES: To structurally characterize a bioengineered construct of FVIII, termed ET3i, which is a human/porcine chimeric B domain-deleted heterodimer with improved expression and slower A2 domain dissociation following proteolytic activation by thrombin. METHODS: The structure of ET3i was characterized with X-ray crystallography and tandem mass spectrometry-based glycoproteomics. RESULTS: Here, we report the 3.2 Å crystal structure of ET3i and characterize the distribution of N-linked glycans with LC-MS/MS glycoproteomics. This structure shows remarkable conservation with the human FVIII protein and provides a detailed view of the interface between the A2 domain and the remaining FVIII structure. With two FVIII molecules in the crystal, we observe two conformations of the C2 domain relative to the remaining FVIII structure. The improved model and stereochemistry of ET3i served as a scaffold to generate an improved, refined structure of human FVIII. With the original datasets at 3.7 Å and 4.0 Å resolution, this new structure resulted in improved refinement statistics. CONCLUSIONS: These improved structures yield a more confident model for next generation engineering efforts to develop FVIII therapeutics with longer half-lives, higher expression levels and lower immunogenicity.

Strontium transport contributes to degradation mechanisms in SOFCs, especially strontium zirconate formation at the interface of the cathode barrier layer with the YSZ electrolyte. High temperatures required for cathode sintering lead to Sr transport during cell construction. SEM analysis of SOFCs with LSCF cathodes shows Sr at the YSZ/GDC barrier layer interface, but no Sr throughout the GDC barrier layer itself, as would be expected for solid-phase transport. Vapor-phase transport was identified as a possible mechanism that would lead to these observations. A series of tests were performed to differentiate between surface diffusion and vapor-phase diffusion of species from LSCF cathode material at typical sintering temperatures (up to 1100°C). A GDC substrate was printed with LSCF and separated by an air gap from a YSZ target substrate. First a simple spacer ring was used to create the air gap, and strontium transport was observed via SEM-EDS (energy dispersive spectroscopy). Then, various geometries with long surface paths were employed to reduce the possibility of surface transport. The target substrates were analyzed via x-ray photoelectron spectroscopy (XPS) with high sensitivity for surface species. An open air gap did not show evidence of Sr or Co transport. A refined, enclosed air gap with long surface path length did show such evidence for Sr and Co, indicating an enclosed area to maintain significant vapor pressure was necessary for transport. An SOFC with LSCF in direct contact with a barrier layer would also provide such an environment for vapor-phase transport to occur. Furthermore, spatially resolved analysis showed a relatively uniform distribution of Sr and Co across the target substrate. This supports the vapor-phase mechanism as Sr and Co transported via surface diffusion would have been fixed preferentially to the outer edge of the target substrate. These results have implications for adjusting sintering conditions and barrier layer requirements to prevent the formation of undesired strontium zirconate. This work was performed for the US DOE Office of Fossil Energy’s Solid Oxide Fuel Cell program under the Cathode Task.

A research and development program is under way at the Pacific Northwest National Laboratory to develop, fabricate and demonstrate operation of an efficient solid oxide electrolyzer stack capable of producing hydrogen from steam. The focus is on reducing the stack manufacturing costs that could be achieved via employing advanced fabrication techniques to reduce the cell area-specific resistances, component thicknesses, and material volumes. This presentation will provide an overview of the progress on cell development, cell size scale-up, cell electrochemical testing, long term durability assessment, and post-test characterization. The data obtained using both small and large size cells will be compared. 2D and 3D models are being constructed to predict expected thermal and electrical performance of SOEC stack.

This study is to complement an early report (the manuscript is attached for review purpose) on the role of interlayer on activity and performance stability in praseodymium nickelates. The aforementioned report showed a remarkable 48% increase in power density while switching from common GDC interlayer to a new interlayer chemistry (PGCO). Furthermore, a stable long-term performance was linked with suppressed reaction between the cathode and PGCO interlayer. In this article, we report in situ studies of the phase evolution. The high energy XRD studies at a synchrotron source showed fully suppressed phase transition in praseodymium nickelates with PGCO interlayer, while the electrodes on the GDC interlayer undergo substantial phase transformation. Furthermore, in operando and post-test XRD analyses shown fully suppressed structural changes in electrodes operated in full cells at 750 degrees C and 0.80 V for 500 hours. SEM-EDS analysis showed that the formation of PrOx at the cathode-interlayer interface may play a role in a decrease of mechanical integrity of the interfaces, due to thermal expansion mismatch, leading to a local stress between the two phases. Consequently, phase evolution at a narrow interface may propagate toward the electrode bulk, leading to structural changes and performance degradation. (C) The Author(s) 2017. Published by ECS. All rights reserved.

Pacific Northwest National Laboratory (PNNL), in collaboration with government agencies and industries, is actively engaged in the development, testing, and characterization of high efficiency, low cost modular solid oxide fuel cell power generation systems for stationary, automotive and military applications. Advanced SOFC systems are being developed which will offer ease of operation on a variety of gaseous liquid hydrocarbon and coal-derived fuels as well as "zero emissions" capability. SOFC R&D activities at PNNL continue in the areas of cell component materials, electrochemistry, cell design and modeling, high temperature corrosion, and fuel processing. Specific activities include development of optimized materials and cost effective fabrication techniques for high power density anode-supported cells operating at temperatures below 800 degrees C, characterization of processes responsible for high electrical performance and long term performance degradation, optimization and cell and stack designs using computational engineering models, and hydrocarbon fuel processing using micro technology.

Solid oxide electrolysis cells (SOEC) operating at 600 – 850°C are used to split water using excess renewable or nuclear electrical energy and convert it to chemical energy which is stored in H2 and O2. SOECs can also be used as electrochemical reactors for the co-electrolysis of steam and carbon dioxide. The two reactants, typically waste products in an industrial plant, could be turned into syngas (CO+H2), a valuable and very commonly used reagent in the chemical industry. Syngas is subsequently used to produce synthetic fuels, olefins or other liquid hydrocarbons via Fischer-Tropsch synthesis or for methanol synthesis and hydroformylation. In this presentation we focus on CO2-H2O co-electrolysis, the simultaneous electrochemical reduction of carbon dioxide and steam, carried out on the porous Ni-based electrodes in high temperature SOECs. Experiments were conducted using multiple button cells. The rate of the electrochemical reactions was measured in the temperature range 700-850oC for varied reactant compositions: 10-98% CO2 and 5-50% H2O, also in the presence of some H2 and CO. Kinetics of electrochemical CO2 reduction were evaluated for different CO2/H2O ratios and compared to steam electrolysis. Product analysis was completed using gas chromatography. Long term electrochemical performance of multiple cells was recorded simultaneously for over 500 hours of continuous testing with occasional interruptions to obtain current-voltage characteristics and collect the impedance spectra. The ability to control H2 :CO ratios in generated syngas by varying the inlet H2O/CO2 ratios and cell potential was demonstrated. Thus, precise control of the H2 to CO ratios, a unique feature of electrochemical conversion can be used to optimize selectivity of the desired byproduct.

Solid oxide electrolysis cells (SOEC) operating at 600 – 850°C are used to split water using excess renewable or nuclear electrical energy and convert it to chemical energy which is stored in H2 and O2. SOECs can also be used as electrochemical reactors for the co-electrolysis of steam and carbon dioxide. The two reactants, typically waste products in an industrial plant, could be turned into syngas (CO+H2), a valuable and very commonly used reagent in the chemical industry. Syngas is subsequently used to produce synthetic fuels, olefins or other liquid hydrocarbons via Fischer-Tropsch synthesis or for methanol synthesis and hydroformylation. In this presentation we focus on CO2-H2O co-electrolysis, the simultaneous electrochemical reduction of carbon dioxide and steam, carried out on the porous Ni-based electrodes in high temperature SOECs. Experiments were conducted using multiple button cells. The rate of the electrochemical reactions was measured in the temperature range 700-850oC for varied reactant compositions: 10-98% CO2 and 5-50% H2O, also in the presence of some H2 and CO. Kinetics of electrochemical CO2 reduction were evaluated for different CO2/H2O ratios and compared to steam electrolysis. Product analysis was completed using gas chromatography. Long term electrochemical performance of multiple cells was recorded simultaneously for over 500 hours of continuous testing with occasional interruptions to obtain current-voltage characteristics and collect the impedance spectra. The ability to control H2 :CO ratios in generated syngas by varying the inlet H2O/CO2 ratios and cell potential was demonstrated. Thus, precise control of the H2 to CO ratios, a unique feature of electrochemical conversion can be used to optimize selectivity of the desired byproduct.

A button solid oxide fuel cell with a La 0.6 Sr 0.4 Co 0.2 Fe 0.8 O 3 cathode and a nickel-YSZ anode was tested over a range of temperatures from 650 to 800 °C and a range of pressures from 101 to 724 kPa. The fuel was simulated steam-reformed kerosene and the oxidant was air. The observed increases in open circuit voltages (OCVs) at elevated pressures were accurately predicted by the Nernst equation. Kinetics also increased with the pressure, although the power boost due to improved kinetics was just more than half as large as the boost due to increased OCV. The power boost increased almost linearly with the logarithm of pressure. At constant voltage the relative power boost due to increased pressure was higher at higher temperatures. At constant current the relative power boost was the same for all temperatures. When the pressure was increased from 101 to 724 kPa, the total power boost at 750 °C and 0.8 V was 66%. A significant decrease in electrodic losses at elevated pressures was observed by impedance spectroscopy. Complex impedance spectra were dominated by a combination of low frequency processes that decreased markedly with increasing pressure. A composite of high-frequency processes also decreased with pressure, but to a lesser extent.

The sodium–nickel chloride (ZEBRA) battery is operated at relatively high temperature (250–350 °C) to achieve adequate electrochemical performance. Reducing the operating temperature in the range of 150200 °C can not only lead to enhanced cycle life by suppressing temperature-related degradations, but also allow the use of lower cost materials for construction. To achieve adequate electrochemical performance at lower operating temperatures, reduction in ohmic losses is required, including the reduced ohmic resistance of β″-alumina solid electrolyte (BASE) and the incorporation of low melting point secondary electrolytes. In present work, planar-type Na/NiCl 2 cells with a thin BASE (600 μm) and low melting point secondary electrolyte were evaluated at reduced temperatures. Molten salts used as secondary electrolytes were fabricated by the partial replacement of NaCl in the standard secondary electrolyte (NaAlCl 4 ) with other lower melting point alkali metal salts such as NaBr, LiCl, and LiBr. Electrochemical characterization of these ternary molten salts demonstrated improved ionic conductivity and sufficient electrochemical window at reduced temperatures. Furthermore, Na/NiCl 2 cells with 50 mol% NaBr-containing secondary electrolyte exhibited reduced polarizations at 175 °C compared to the cell with the standard NaAlCl 4 catholyte. The cells also exhibited stable cycling performance even at 150 °C.

A Ca- and Co-doped yttrium chromite (YCCC) - samaria-doped ceria (SDC) composite was studied in relation to a potential use as a solid oxide fuel cell (SOFC) anode material. Tests performed using the yttria-stabilized zirconia (YSZ) electrolyte-supported cells revealed that the electrocatalytic activity of the YCCC-SDC anode towards hydrogen oxidation at 800 C was comparable to that of the Ni-YSZ anode. In addition, the YCCC-SDC anode exhibited superior sulfur tolerant characteristics showing less than 10% increase in a polarization resistance, fully reversible, upon exposure to 20 ppm H2S at 800 C. No performance degradation was observed during multiple reduction-oxidation (redox) cycles when the anode was intentionally exposed to the air environment followed by the reduction in hydrogen. The redox tolerance of the YCCC-SDC anode was attributed to the dimensional and chemical stability of the YCCC exhibiting minimal isothermal chemical expansion upon redox cycling.

The interactions of antimony with the nickel–zirconia anode in solid oxide fuel cells (SOFCs) have been investigated. Tests with both anode-supported and electrolyte-supported button cells were performed at 700 and 800 °C in synthetic coal gas containing 100 ppb to 9 ppm antimony. Minor performance loss was observed immediately after Sb introduction to coal gas resulting in ca. 5% power output drop. While no further degradation was observed during the following several hundred hours of testing, cells abruptly and irreversibly failed after 800–1600 h depending on Sb concentration and test temperature. Antimony was found to interact strongly with nickel resulting in extensive alteration phase formation, consistent with expectations based on thermodynamic properties. Nickel antimonide phases, NiSb and Ni 5 Sb 2 , were partially coalesced into large grains and eventually affected electronic percolation through the anode support. Initial degradation was attributed to diffusion of antimony to the active anode/electrolyte interface to form an adsorption layer, while the late stage degradation was due the Ni–Sb phase formation. Assuming an average Sb concentration in coal gas of 0.07 ppmv, a 500 μm thick Ni/zirconia anode-supported cell is not expected to fail within 7 years when operated at a power output of 0.5 W cm −2 and fuel utilization above 50%.

Oxidation-resistant alloys find use as interconnect materials, heat exchangers, and gas supply tubing in solid oxide fuel cell (SOFC) systems, especially when operated at temperatures below ∼800 °C. If fueled with synthesis gas derived from coal or biomass, such metallic components could be exposed to impurities contained in those fuel sources. In this study, coupons of ferritic stainless steels Crofer 22 APU and SS 441, austenitic nickel–chromium superalloy Inconel 600, and an alumina-forming high nickel alloy alumel were exposed to synthesis gas containing ≤2 ppm phosphorus, arsenic and antimony, and reaction products were tested. Crofer 22 APU coupons coated with a (Mn,Co) 3 O 4 protective layer were also evaluated. Phosphorus was found to be the most reactive. On Crofer 22 APU, the (Mn,Cr) 3 O 4 passivation layer reacted to form an Mn–P–O product, predicted to be manganese phosphate from thermochemical calculations, and Cr 2 O 3 . On SS 441, reaction of phosphorus with (Mn,Cr) 3 O 4 led to the formation of manganese phosphate as well as an Fe–P product, predicted from thermochemical calculations to be Fe 3 P. Minimal interactions with antimony or arsenic in synthesis gas were limited to Fe–Sb and Fe–As solid solution formation. Though not intended for use on the anode side, a (Mn,Co) 3 O 4 spinel coating on Crofer 22 APU reacted with phosphorus in synthesis gas to produce products consistent with Mn 3 (PO 4 ) 2 and Co 2 P. A thin Cr 2 O 3 passivation layer on Inconel 600 did not prevent the formation of nickel phosphides and arsenides and of iron phosphides and arsenides, though no reaction with Cr 2 O 3 was apparent. On alumel, an Al 2 O 3 passivation layer rich in Ni did not prevent the formation of nickel phosphides, arsenides, and antimonides, though no reaction with Al 2 O 3 occurred. This work shows that unprotected metallic components of an SOFC stack and system can provide a sink for P, As and Sb impurities that may be present in fuel gases, and thus complicate experimental studies of impurity interactions with the anode.

The performance of anode-supported solid oxide fuel cells (SOFC) was evaluated in synthetic coal gas containing HCl in the temperature range 650–850 °C. Exposure to up to 800 ppm HCl resulted in reversible poisoning of the Ni/zirconia anode by chlorine species adsorption, the magnitude of which decreased with increased temperature. Performance losses increased with the concentration of HCl to ∼100 ppm, above which losses were insensitive to HCl concentration. Neither cell potential, nor current density had any effect on the extent of poisoning. No evidence was found for long-term degradation that can be attributed to HCl exposure. Similarly, no evidence of microstructural changes or formation of new solid phases as a result of HCl exposure was found. From thermodynamic calculations, solid nickel chloride phase formation was shown to be highly unlikely in coal gas containing HCl. The presence of HCl at even the highest anticipated concentrations in coal gas would minimally increase the volatility of nickel.

The interaction of phosphorus in synthetic coal gas with the nickel-based anode of solid oxide fuel cells has been investigated. Tests with both anode-supported and electrolyte-supported button cells were performed at 700 to 800 °C in synthetic coal gas containing 0.5 to 10 ppm phosphorus, which was introduced as phosphine. Two primary modes of degradation were observed. The most obvious was the formation of a series of bulk nickel phosphide phases, of which Ni 3 P, Ni 5 P 2 , Ni 12 P 5 and Ni 2 P were identified. Phosphorus was essentially completely captured by the anode, forming a sharp boundary between converted and unconverted anode portions. These products partially coalesced into large grains, which eventually affected electronic percolation through the anode support. From thermodynamic calculations, formation of the first binary nickel phosphide phase is possible at phosphorus concentrations

Performance of solid oxide fuel cell (SOFC) with nickel/zirconia anodes on synthetic coal gas in the presence of low levels of phosphorus, arsenic, selenium, sulfur, hydrogen chloride, and antimony impurities were evaluated. The presence of phosphorus and arsenic led to the slow and irreversible SOFC degradation due to the formation of secondary phases with nickel, particularly close to the gas inlet. Phosphorus and antimony surface adsorption layers were identified as well. Hydrogen chloride and sulfur interactions with the nickel were limited to the surface adsorption only, whereas selenium exposure also led to the formation of nickel selenide for highly polarized cells.

The performance of anode-supported and electrolyte-supported solid oxide fuel cells was investigated in synthetic coal gas containing 0–10 ppm arsenic at 700–800 °C. Arsenic was found to interact strongly with nickel, resulting in the formation of nickel–arsenic solid solution, Ni5As2 and Ni11As8, depending on temperature, arsenic concentration, and reaction time. For anode-supported cells, loss of electrical connectivity in the anode support was the principal mode of degradation, as nickel was converted to nickel arsenide phases that migrated to the surface to form large grains. Cell failure occurred well before the entire anode was converted to nickel arsenide, and followed a reciprocal square root of arsenic partial pressure dependence that is consistent with a diffusion-based rate-limiting step. Failure occurred more quickly with electrolyte-supported cells, which have a substantially smaller nickel inventory. For these cells, time to failure varied linearly with the reciprocal arsenic concentration. Failure occurred when arsenic reached the anode/electrolyte interface, though agglomeration of nickel reaction products may have also contributed. Test performed with nickel/zirconia coupons showed that arsenic was essentially completely captured in a narrow band near the fuel gas inlet. Arsenic concentrations of ∼10 ppb or less are estimated to result in acceptable rates of fuel cell degradation.

The operation of solid oxide fuel cells (SOFC) was evaluated on simulated coal gas in the presence of several coal gas impurities that are expected to remain in low concentration after warm gas cleanup. Phosphorus, arsenic and sulfur were considered in this study. The presence of phosphorus and arsenic in low, 1-2 ppm, concentrations led to the slow and irreversible SOFC degradation due to the formation of the secondary phases with nickel in the upper part of the nickel-based anode close to the gas inlet. Sulfur interactions with the nickel were limited to the surface only. Cell performance losses due to sulfur exposure were reversible and independent of the presence of other impurities.

Thermal cycle and exposure tests were conducted on ceramic-to-metal joints prepared by a new sealing technique. Known as reactive air brazing, this joining method is currently being considered for use in sealing various high-temperature solid-state electrochemical devices, including planar solid oxide fuel cells (pSOFC). In order to simulate a typical pSOFC application, test specimens were prepared by joining ceramic anode/electrolyte bilayers to metal washers, of the same composition as the common frame materials employed in pSOFC stacks, using a filler metal composed of 4 mol% CuO in silver. The brazed samples were exposure tested at 750 °C for 200, 400, and 800 h in both simulated fuel and air environments and thermally cycled at rapid rate (75 °C min −1 ) between room temperature and 750 °C for as many as 50 cycles. Subsequent joint strength testing and microstructural analysis indicated that the samples exposure tested in air displayed little degradation with respect to strength, hermeticity, or microstructure out to 800 h of exposure. Those tested in fuel showed no change in rupture strength or loss in hermeticity after 800 h of high-temperature exposure, but did undergo microstructural change due to the dissolution of hydrogen into the silver-based braze material. Air-brazed specimens subjected to rapid thermal cycling exhibited no loss in joint strength or hermeticity, but displayed initial signs of seal delamination along the braze–electrolyte interface after 50 cycles.

A surfactant templated mesoporous silica thin film is essentially an air-silica composite, with mechanical properties dominated by the more rigid component: the silica mesopore walls. It is often convenient to assume that mesopore wall properties are those of fused silica. However, we measured substantial reductions in wall density and elastic modulus (Ewall), due to incomplete silica condensation. Elastic moduli (Efilm) of disordered (sponge-like) and ordered (honeycomb-like) thin films were measured by nanoindentation. Curve fits to the well-known modulus vs. film porosity (P) correlation, Efilm/Ewall = (1-P)n, gave a higher n = 2.5 for the sponge-like film, but a lower n = 2.2 for the honeycomb-like film, in contrast to theoretical expectations (n = 2 for sponge-like and n = 3 for honeycomb-like). Although properties such as the dielectric constant depend primarily on first-order structural information (P), the elastic modulus of structurally imperfect films may require second-order (pore wall thickness/diameter ratio) and third-order (pore connectivity) parameters to explain the data. The power law exponent n can vary continuously, depending on the details of the mesostructure.

Among the various SOFC stack designs under development worldwide, the planar configuration has received growing attention because of its compact nature and associated high volumetric power density - design features which are essential in transportation applications. With the advent of anode-supported cells that employ thin YSZ electrolytes, these devices can be operated at reduced temperatures (700 - 800°C) and still achieve the same current densities exhibited by their high-temperature, thick electrolyte-supported counterparts. The lower operating temperature not only makes it possible to consider inexpensive, commercially available high temperature alloys for use in the stack and balance of plant, but also expands the list of materials/techniques that could be employed in device sealing. Here we discuss two such methods that may have potential application in pSOFCs.

Nhlh2 is a member of the basic helix-loop-helix (bHLH) transcription factor family and is expressed in developing and adult neuroendocrine tissues such as the pituitary and hypothalamus. Targeted deletion of Nhlh2 (N2KO) in mice results in hypogonadism and obesity. While gonadally intact male N2KO mice are infertile and lack male sexual behavior, female N2KO mice can become pregnant and carry litters to full term. Unlike normal females in which fertility averages 8–12 months with approximately one pregnancy per month, N2KO females have a shorter reproductive span with most females supporting only three to four pregnancies in a 9-month period. In addition, N2KO females exhibit abnormal estrous cycles characterized by a truncated estrus and a prolonged proestrus. We have found that while young female N2KO mice ovulate the same number of oocytes as normal females in response to exogenous hormones, the number of oocytes released by aged N2KO females is reduced over 50%. Interestingly, oocytes from N2KO females are equally competent for in vitro fertilization assays when compared to oocytes from similarly aged normal and heterozygous mice. We have further demonstrated that both young and old N2KO females show at least a 50% reduction in hormone-stimulated sexual behavior as measured by their lordosis quotient. This suggests that N2KO females show a lifelong behavioral hyporesponsiveness to exogenous steroid hormones accompanied by a reduction in reproductive longevity via reduced ovulation with aging. Potential gene regulatory mechanisms that involve the action of the Nhlh2 transcription factor on female fertility and sexual behavior are discussed.

One of the critical issues in designing and fabricating high-performance planar solid oxide fuel cell (pSOFC) stacks is the ability to hermetically seal adjacent metal and ceramic components. In our pSOFC development program, we have designed a testing technique that allows us to screen through the numerous variables involved in developing glass seals. Using this test for example, we have found that the composition of the metal component plays an important role in the strength of the seal. Microstructural analysis of as-sealed specimens revealed that an interfacial reaction zone forms during joining, and it appears that the thickness and composition of this layer are the dominant parameters that control joint strength. In this paper the details of the seal test are reported. The results have proven particularly significant in the development of the next-generation stack design. Supporting microstructural and chemical analyses collected on the test specimens are also presented and used to interpret the seal test results in an effort to identify the necessary steps toward improving glass pSOFC seals.

One of the challenges in manufacturing planar solid oxide fuel cells (pSOFCs) is in hermetically sealing the ceramic and metallic components such that the resulting joint remains rugged and stable over the lifetime of the stack. Traditionally, glass joining or compressive sealing has been used. While short-term success has been achieved with these techniques, it is apparent that to meet the long-term operational needs of stack designers, alternative sealing concepts will need to be conceived. At Pacific Northwest National Laboratory we have been developing two such alternatives, air brazing and bonded compliant sealing, the details of which are outlined here.

Delphi and Battelle are developing a solid oxide fuel cell (SOFC) stack for transportation and stationary applications. This team is part of the Solid State Energy Conversion Alliance (SECA) initiative. This paper describes the status of development of the Generation 2 stack and key progress made in addressing some of the challenges in this technology.

Targeted deletion of the neuronal basic helix-loop-helix transcription factor Nhlh2 results in adult-onset obesity in mice. Measurement of body weight and body composition in animals aged 3-25 weeks indicates that while male and female Nhlh2 knockout (N2KO) animals both show adult-onset obesity, the time frame for development of obesity is different, with females becoming obese by 7 weeks of age and males becoming obese by 10 weeks of age. Heterozygous (HET) animals also become obese but with a slower onset, indicating a dosage effect for the activity of the Nhlh2 transcription factor. Food intake, body temperature, and voluntary activity were measured in both preobese and obese N2KO, HET, and wild-type (WT) animals to determine which factors contributed to weight gain. While increased food intake and decreased body temperature were found in older obese N2KO animals, only reduced physical activity preceded the onset of obesity in N2KO mice. N2KO animals had no deficit in either circadian rhythm or balance and motor control, indicating that reduced voluntary activity is the result of a behavioral change. These data demonstrate a role for the Nhlh2 transcription factor in controlling genes important to energy expenditure, and more specifically voluntary physical activity of animals.

The use of doped ceria as an interlayer in solid oxide fuel cells (SOFCs) is ubiquitous, which provides better thermal expansion match and prevents interaction between the cathode (e.g. LSCF) and electrolyte (e.g. YSZ). However, the role of ceria interlayer on the cathode phase durability and catalytic activity remains obscure. This is particularly true in nickelate cathodes (e.g. Pr2NiO4). Here, we report that traditional Gd-doped ceria (GDC) interlayer substantially accelerates the phase transition in Pr2NiO4. Two new interlayer designs were investigated in order to circuvent the phase evolution by using (1) a thin Pr6O11 film deposited on the surface of GDC, and (2) a Pr-doped ceria interlayer. The latter design not only suppresses the phase transition, but also results in a 48% increase in cathode performance; and more importantly, it leads to a zero degradation over long-term measurements. Systemetic in situ and post analyses were carried out to understand the mechanism, by which the interlayer affects the cathode durability and activity. This material is based upon work supported by the U.S. Department of Energy under Award Number DE-FE0023475.

A test fixture and methodology was developed for testing anode-supported SOFC button cells downstream from a chromia pellet placed in the cathode air stream at a prescribed temperature to control volatilization of Cr vapor species. A porous alumina foam coated with a Cr gettering material is then placed downstream from the cell to capture Cr from the cathode air stream. The Cr gettering coating is composed of Na2CO3, which reacts with Cr vapor species to form Na2CrO4. The coating and its reaction product are both water soluble which facilitates dissolving them from the porous substrate for subsequent ICP analysis to determine the concentration of the resulting aqueous solution. The mass of collected Cr can then be calculated and used to determine the average concentration in the known volume of air that flowed past the cathode over the duration of the test. Electrochemical tests of cells with LSM/YSZ cathodes were performed with the chromia pellet at varying conditions of temperature and humidity to elicit various levels of Cr volatility. Multiple cells were tested at each condition for 600 to 1000 hours. Molar concentrations of Cr in the cathode air as small as 4×10-11 were found to cause ~4%/kh degradation in performance.

Solid oxide fuel cells (SOFCs) with lanthanum strontium cobalt ferrite (LSCF) cathodes often employ a samaria-doped or gadolinia-doped ceria (SDC or GDC, respectively) barrier layer between the cathode and the yttria-stabilized zirconia (YSZ) electrolyte to inhibit Sr from migrating to the YSZ surface where it reacts to form electrically-resistive strontium zirconate during cathode sintering. Because the SDC must be sintered at limited temperatures (generally ≤1200°C) to avoid forming a CeO2-ZrO2 solid solution that has significantly lower ionic conductivity, screen printed barrier layers are often porous after firing. Electrochemical tests of cells with dense, continuous pulsed laser deposited (PLD) SDC found that these cells exhibited significantly higher performance than those with the conventional screen-printed porous SDC layers. Thus, PNNL began investigating the fabrication of dense, continuous SDC barrier layers using cost-effective deposition by screen printing which is amenable to industrial production of SOFCs. Many approaches to improve the SDC density have been explored including the use of powder with reduced particle sizes, inks with increased solids loading, and doping with sintering aids. While some of these tests were successful in enhancing the density of the SDC, the stresses induced by constrained sintering on the surface of previously-fired YSZ caused cracks and discontinuities in the SDC barrier layer. These results together with steps that have been taken to address the constrained sintering issue will be presented.

One of the key limiting issues in designing and fabricating a high performance planar solid oxide fuel cell (pSOFC) stack is the development of the appropriate materials and techniques for hermetically sealing the metal and ceramic components. There are essentially two standard methods of sealing: (1) by forming a rigid joint or (2) by constructing a compressive “sliding” seal. While short-term success has been achieved with both techniques, it is apparent that to meet the long-term operational needs of stack designers, alternative sealing concepts will need to be conceived. Described below are two alternative pSOFC sealing methods that have been developed at Pacific Northwest National Laboratory.

Developing reliable, hermetic ceramic-to-metal seals has become a key issue to the future success of planar solid oxide fuel cell (pSOFC) technology. In the course of designing and fabricating operating pSOFC stacks at Pacific Northwest National Laboratory over the past several years, we have relied on a simple, but extremely useful seal testing technique that allows us to screen through the numerous variables involved in developing glass seals. Here we discuss the design of the test apparatus and the procedure we employed when using the test to analyze the effects of various processing parameters on the hermeticity and durability of our glass seals.

In mice, targeted deletion of the basic helix-loop-helix transcription factor, nescient helix-loop-helix 2 (Nhlh2), leads to adult-onset obesity and reduced physical activity. We propose the novel hypothesis that transcriptional activity by Nhlh2 (NHLH2 in humans) controls either the ability or the motivation for exercise.

This report describes efforts to characterize the interactions nickel anodes with phosphorus in coal gas using three different button cell configurations to emphasize particular degradation modes. Important parameters addressed included contaminant concentration, temperature, reaction time, fuel utilization, and current density. In addition, coupon tests in flow-through and flow-by arrangements were conducted to complement cell tests. The studies have involved extensive electrochemical testing using both dc and ac methods. Post-test analyses to determine the composition and extent of nickel modification are particularly important to understanding reactions that have occurred. This report also provides a thermodynamic assessment of contaminant reactions with nickel in a coal gas environment with regard to alteration phase formation. Contaminants addressed were phosphorus, arsenic, sulfur, selenium, and antimony. Phosphorus was found to interact strongly with nickel and result in extensive alteration phase formation, consistent with expectations based on thermodynamic properties. Even in button cell tests where the fuel utilization was low, phosphorus was found to be nearly completely captured by the nickel anode. For anode-supported cells, an important degradation mode involved loss of electronic percolation, the result of nickel phosphide formation, grain growth, and inducement of micro-fractures within the anode support. Even with excessive anode support conversion, electrochemicalmore » degradation rates were often very low. This is attributed to a “shadowing effect,” whereby a dense structure such as current leads prevent phosphorus from reacting with the nickel directly underneath. This effect maintains an electrical pathway to the active interface, and allows the cell to operate with minimal degradation until the anode is essentially completely consumed. In a planar stack, ribs on the interconnect plate would be expected to provide this conductive pathway in the event of phosphorus exposure. When phosphorus interactions proceeded to the active interface, most easily observed in tests with electrolyte-supported cells having a thin anode, the electrochemical performance decreased considerably.« less

The Tub gene was originally identified as a spontaneous mutation in C57Bl/6J mice, and associated with adult-onset obesity (Tub MUT mice). Although the original Tub MUT mouse was identified over 15 years ago, there have been few reports on the animal's food intake, body fat percentage or energy expenditure. In this study, we report food intake, body weight from 5-20 weeks, body fat, body temperature and three different measures of physical activity behavior. Tub MUT mice display reduced food intake, uncharacteristic of many obese mouse models, and reduced voluntary wheel running with normal home cage ambulatory behavior. We conclude that motivation for food and exercise is an underlying defect in TUB MUT mice.

A significant challenge in developing and manufacturing planar solid oxide fuel cells is in hermetically sealing the electrochemically active ceramic PEN to the metallic body of the device. One means of doing this is by chemically bonding the electrolyte surface of the PEN to the metal frame, thus forming a fixed or static seal. Typically a glass or glass-ceramic material is used in making this type of seal. However because of their brittle nature, there are number of manufacturing and operational problems that are encountered when using these materials. In an effort to efficiently screen potential solutions to these problems, a seal rupture test was developed. Details of the test procedure, the test device, and its use in thermal cycle testing various planar solid oxide fuel cell sealing concepts will be discussed.

As interest in high temperature electrochemical membrane devices for energy and gas generation has intensified, it has become apparent that developing an appropriate method of hermetically joining the ceramic and metallic components in these devices will be critical to their success. A recently developed technique referred to as reactive air brazing (RAB) has shown promise in the joining of components for planar solid oxide fuel cells (pSOFC) and oxygen generators. In the study described below, the relationship between braze composition, substrate wetting, and joint strenth was investigated to gain further understanding of the RAB process. It was found that braze wettability and joint strength are inversely related for the simple binary Ag-CuO braze system.

Spin-on mesoporous silica films were prepared on eight-inch wafers at SEMATECH by condensation of a silicate network around surfactant micellar structures. Copper single-damascene one-level test structures were built using mesoporous silica as the intermetal dielectric. No major structural failures were observed after chemical mechanical planarization on both blanket films and patterned wafers, indicating relatively good mechanical integrity for a highly porous structure. A simple silane spin-coating step used at SEMATECH on the films appears to be insufficient for complete dehydroxylation and silylation. The electrical test results on the metal comb structures showed good capacitance and leakage current distributions. However, capacitance and leakage current changes were observed after each post-CMP process step, and these changes could be correlated to moisture desorption/outgassing, which was also noted during k measurement. With controlled film synthesis and dehydroxylation conditions, mesoporous silica films with k ≤2.0 and elastic modulus of 4.0 GPa have been synthesized at PNNL. The results of the Cu one-level metal screening tests at SEMATECH combined with properties obtained at PNNL indicate that mesoporous molecularly-templated silicate films hold promise as ultra low k intermetal dielectrics.

The Advanced Airborne Hyperspectral Imaging System (AAHIS) is a compact, lightweight visible and near IR pushbroom hyperspectral imaging spectrometer flown on a Piper Aztec aircraft. AAHIS is optimized for use in shallow water, littoral, and vegetation remote sensing. Data are collected at up to 55 frames/second and may be displayed and analyzed inflight or recorded for post-flight processing. Swath width is 200 meters at a flight altitude of 1 km. Each image pixel contains hyperspectral data simultaneously recorded in up to 288 contiguous spectral channels covering the 432 to 832 nm spectral region. Pixel binning typically yields pixels 1.0 meter square with a spectral channel width of 5.5 nm. Design and performance of the AAHIS is presented, including processed imagery demonstrating feature detection and materials discrimination on land and underwater at depths up to 27 meters.© (1995) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

Three distinctly different characteristic responses of a nickel/yttria-stabilized zirconia (Ni/YSZ) cermet anode to the presence of hydrogen selenide in synthetic coal gas were observed, depending on temperature (650-800oC), H2Se concentration (0-40 ppm), and especially on the extent of anodic polarization (0 to ~0.5 V). The first level of response was characterized by a rapid but modest decrease in power density to a new steady state, with no further degradation observed in tests up to 700 hours in duration. Mostly observed at high temperatures, low H2Se concentrations, and low anodic polarizations, this response level was similar to effects caused by the presence of H2S, but with slower onset and lower reversibility. Higher anodic polarization at a constant current could trigger a second level of response characterized by oscillatory behavior involving cycles of rapid performance loss followed by rapid recovery. Oscillations at the constant current density were accompanied by the appearance and disappearance of a new feature in the electrochemical impedance spectrum with a summit frequency of ~100 Hz. Oscillatory behavior ceased when the current density was lowered. Such behavior was not observed for cells operated at a constant potential of similar magnitude, though. A third level of response, irreversible cell failure,more » could be induced by further increases in anodic polarization, additionally favored by low temperature and high H2Se concentration. Post-test analyses of failed cells by electron microscopy revealed the extensive microstructural changes including the appearance of nickel oxide and nickel selenide alteration phases, only at the anode/electrolyte interface. From bulk thermochemical considerations the formation of nickel selenides could not be expected. Local chemical conditions created at the anode/electrolyte interface appear to be of overriding importance with respect to the extent of Ni/YSZ anode interactions with H2Se in coal gas.« less

The structural, thermal and electrical characteristics of calcium- and cobalt-doped yttrium chromites were studied for a potential use as the interconnect material in high temperature solid oxide fuel cells (SOFCs) as well as other high temperature electrochemical and thermoelectric devices. The Y0.8Ca0.2Cr1-xCoxO3±δ (x=0, 0.1, 0.2, 0.3) compositions had single phase orthorhombic perovskite structures in the wide range of oxygen pressures. Sintering behavior was remarkably enhanced upon cobalt doping and densities 95% and 97% of theoretical density were obtained after sintering at 1300oC in air, when x was 0.2 and 0.3, respectively. The electrical conductivity in both oxidizing and reducing atmospheres was significantly improved with cobalt content, and values of 49 and 10 S/cm at 850oC and 55 and 14 S/cm at 950oC in air and forming gas, respectively, were reported for x=0.2. The conductivity increase was attributed to the charge carrier density increase upon cobalt substitution for chromium confirmed with Seebeck measurements. The thermal expansion coefficient (TEC) was increased with cobalt content and closely matched to that of an 8 mol% yttria-stabilized zirconia (YSZ) electrolyte for 0.1 ≤ x ≤ 0.2. The chemical compatibility between Y0.8Ca0.2Cr1-xCoxO3±δ and YSZ was evaluated firing the two at 1400oC and no reaction products weremore » found if x value was kept lower than 0.2.« less

The ohmic resistance of anode-supported solid oxide fuel cells having a manganese-based cathode was lowered when operated in synthetic coal gas containing hydrogen chloride. This effect was not observed for cells with cathodes that did not contain manganese. Substantial amounts of Mn were found throughout the grain boundaries of the 8 mole% yttria-stabilized zirconia (8YSZ) electrolyte. Exposure to HCl partially removed Mn near the anode/electrolyte interface, presumably by volatilization as MnCl2(g). This work suggests that one of the underlying causes of higher than expected electrolyte resistance in anode-supported SOFCs is a lowering of the ionic conductivity of 8YSZ by incorporation of manganese.

The beneficial effects humidity treatments have on molecularly templated mesoporous silica films with respect to elastic modulus, with minimal detrimental effects on porosity and dielectric constant, were identified.