Understanding the Initial Stages of Reversible Mg Deposition and Stripping in Inorganic Non-Aqueous Electrolytes

Multi-valent (MV) battery architectures based on pairing a Mg metal anode with a high-voltage ($\sim$ 3 V) intercalation cathode offer a realistic design pathway toward significantly surpassing the energy storage performance of traditional Li-ion based batteries, but there are currently only few electrolyte systems that support reversible Mg deposition. Using both static first-principles calculations and $ab\; initio$ molecular dynamics, we perform a comprehensive adsorption study of several salt and solvent species at the interface of Mg metal with an electrolyte of Mg$^{2+}$ and Cl$^-$ dissolved in liquid tetrahydrofuran (THF). Our findings not only provide a picture of the stable species at the interface, but also explain how this system can support reversible Mg deposition and as such we provide insights in how to design other electrolytes for Mg plating and stripping. The active depositing species are identified to be (MgCl)$^+$ monomers coordinated by THF, which exhibit preferential adsorption on Mg compared to possible passivating species (such as THF solvent or neutral MgCl$_2$ complexes). Upon deposition, the energy to desolvate these adsorbed complexes and facilitate charge-transfer is shown to be small ($\sim$ 61 $-$ 46.2 kJ mol$^{-1}$ to remove 3 THF from the strongest adsorbing complex), and the stable orientations of the adsorbed but desolvated (MgCl)$^+$ complexes appear favorable for charge-transfer. Finally, observations of Mg-Cl dissociation at the Mg surface at very low THF coordinations (0 and 1) suggest that deleterious Cl incorporation in the anode may occur upon plating. In the stripping process, this is beneficial by further facilitating the Mg removal reaction

Tailoring the Nanostructure Anodically Formed in the Passive Oxide on Aluminum -Relevance to Localized Corrosion Initiation

Anodic processes at a passive metal surface like aluminum could be envisioned as being initiated or controlled by nano-scale structural changes within the metal's surface oxide. Examples include proposed roles for nanostructure formation in the pit initiation for Al corrosion (1,2), void formation on pit initiation of Al during anodic etching (3), and possibly deformationinduced nanostructure in pore formation in Al (4). Characterizing the nanostructure present in the passive oxide and learning how to control structure formation offers an opportunity to electrochemically explore deterministic relationships between known structure and anodic event initiation. Recent work has shown that voids can nucleate at the aluminum/aluminum oxide interface and grow into the passive oxide at standard slow rate polarization in moderate chloride solutions well below the onset for pit initiation (5). Analytical transmission electron microscopy argues that these voids are encapsulated absence of matter produced by cation and anion vacancy saturation and coalescence in the oxide. Atomic force microscopy coupled with scanning electron microscopy show that these voids can transition to pores at efficiencies up to 20% of the void population or 2x10 10 cm -2 prior to the initiation of pitting. These results demonstrate that interfacial voids are formed as a result of ion transport through the passive oxide and provide a foundation for exploring their role in pit initiation. Most of this work has focused on anhydrous oxides to model the initial passive oxide on Al. These oxides are formed on atomically clean (vacuum prepared) bulk Al surfaces (both single and poly-crystalline) and nanocrystalline evaporated Al films exposed to O 2 at room temperature and atmospheric pressure. The length of time for equilibration of the model oxide in a deaerated electrolyte is the factor that controls the extent to which voids and pores form. Time-of-flight secondary ion mass spectrometric (TOF-SIMS) measurements show that solution equilibration produces a slow growth of the initial 3 nm oxide up to an equilibration value of 4.5 nm over a period of 16 hours. Anodic polarization of the initial oxide produces a near-equivalent final thickness over a much faster time scale. It is this more rapidly formed film that exhibits a larger passive charge density (and larger void and pore densities) that exceeds values expected for uniform growth to its measured limiting thickness. The excess charge density has to be consumed either by vacancy generation (and subsequent coalescence) or dissolution. Dissolution alone appears an unlikely explanation given reported rates in a mixed chloride/borate electrolyte (6). An initial attempt can be made to identify whether these structures play a role in pit initiation by exploiting this equilibration time effect. In limited cases, we have been able to show that higher density void nucleation produced by using shorter equilibration times can lead to high densities of pores that maintain a minimum (< 20 nm) diameter. It is this high density of transitioning features that might be expected to increase the probability of pitting event when compared the absence of detectable pores for long equilibration times. We have observed as much as a 200 mV shift in the stable mean pitting potential to more active values with decreased equilibration time. Where these results provide an indication that voids and pores can contribute to pitting, they do not identify the necessity for these structures in a generalized pitting mechanism. More recent work is focused on exploiting how the passive oxide is formed in an effort to tailor its resulting ion transmission characteristics and range of nanostructure exhibited. Our eventual goal is to learn how to control this nanostructure to a level where statistical studies of current transient events (i.e. metastable pitting events) can be correlated to characteristics of the feature population. Hydrous oxides produced by exposure of atomically clean Al to pure water vapor with and without subsequent dehydration show even larger variation in passive charge density response with anodic polarization. These results indicate that the initial characteristics of the oxide prior to immersion in the electrolyte could provide a wider range of control of structure density and size. The use of alternate electrolytes containing borate produces unique differences in the nanostructure population. One quite interesting effect of the borate anion is that TOF-SIMS and x-ray photoelectron spectroscopy show it attenuates the equilibrium concentration of chloride within the outer layer and/or at the barrier oxide interface in the passive oxide. Electrochemical impedance measurements indicate a reduced defect concentration within the barrier layer when borate is present while electron microscopy shows the void population is suppressed when borate anion is present. These results suggest that electrolyte composition can be used to control the nanostructure population as well

Biochemical evidence for conformational variants in the anti-viral and pro-metastatic protein IFITM1

Interferon induced transmembrane proteins (IFITMs) play a dual role in the restriction of RNA viruses and in cancer progression, yet the mechanism of their action remains unknown. Currently, there is no data about the basic biochemical features or biophysical properties of the IFITM1 protein. In this work, we report on description and biochemical characterization of three conformational variants/oligomeric species of recombinant IFITM1 protein derived from an E. coli expression system. The protein was extracted from the membrane fraction, affinity purified, and separated by size exclusion chromatography where two distinct oligomeric species were observed in addition to the expected monomer. These species remained stable upon re-chromatography and were designated as “dimer” and “oligomer” according to their estimated molecular weight. The dimer was found to be less stable compared to the oligomer using circular dichroism thermal denaturation and incubation with a reducing agent. A two-site ELISA and HDX mass spectrometry suggested the existence of structural motif within the N-terminal part of IFITM1 which might be significant in oligomer formation. Together, these data show the unusual propensity of recombinant IFITM1 to naturally assemble into very stable oligomeric species whose study might shed light on IFITM1 anti-viral and pro-oncogenic functions in cells

Evaluation of the porous silicon capacitor as a moisture sensor for vacuum applications

A growing demand exists for inexpensive and reliable sensors for moisture detection in reduced pressure processing environments. Sandia`s Porous Silicon Capacitor (PSC) sensor appears to be an ideal candidate for this application. This sensor is a solid state device that detects moisture through changes in dielectric constant with water adsorption. Standard microelectronic fabrication techniques are used in its production affording low cost production and ready integration into complex sensor and electronic arrays. This sensor has previously been investigated for moisture detection in fluid streams, however, little effort has been placed on its behavior in a vacuum environment. Sandia`s Sensors in Vacuum (SIV) test facility has been employed to evaluate the performance characteristics of this sensor in vacuum. In addition, a vacuum-based study allows for a more controlled environment in which the intrinsic lower limit for moisture detection and response times to moisture changes can be easily determined quantitatively. This report describes the performance characteristics of a series of sensors from a single production lot. Calibration of these sensors to moisture levels from part per billion to part per hundred concentrations has been performed. The concentration-dependent sensitivity of these sensors is documented. The response time and drift characteristics of these sensors are also discussed. The investigation of a preliminary method for increasing the recovery time of the sensor after moisture exposure is presented. The role of hydrocarbon contamination, a potential problem in some vacuum schemes, is also evaluated. Specific recommendations are made on how to implement this sensor for vacuum applications

Comparative characterization of two monoclonal antibodies targeting canine PD-1

Monoclonal antibodies targeting immune checkpoints have revolutionizedoncology. Yet, the effectiveness of these treatments varies significantly amongpatients, and they are associated with unexpected adverse events, includinghyperprogression. The murine research model used in drug development fails torecapitulate both the functional human immune system and the populationheterogeneity. Hence, a novel model is urgently needed to study theconsequences of immune checkpoint blockade. Dogs appear to be uniquelysuited for this role. Approximately 1 in 4 companion dogs dies from cancer, yetno antibodies are commercially available for use in veterinary oncology. Here wecharacterize two novel antibodies that bind canine PD-1 with sub-nanomolaraffinity as measured by SPR. Both antibodies block the clinically crucial PD-1/PDL1 interaction in a competitive ELISA assay. Additionally, the antibodies weretested with a broad range of assays including Western Blot, ELISA, flowcytometry, immunofluorescence and immunohistochemistry. The antibodiesappear to bind two distinct epitopes as predicted by molecular modeling andpeptide phage display. Our study provides new tools for canine oncologyresearch and a potential veterinary therapeutic

Modelling mutational landscapes of human cancers in vitro

Experimental models that recapitulate mutational landscapes of human cancers are needed to decipher the rapidly expanding data on human somatic mutations. We demonstrate that mutation patterns in immortalised cell lines derived from primary murine embryonic fibroblasts (MEFs) exposed in vitro to carcinogens recapitulate key features of mutational signatures observed in human cancers. In experiments with several cancer-causing agents we obtained high genome-wide concordance between human tumour mutation data and in vitro data with respect to predominant substitution types, strand bias and sequence context. Moreover, we found signature mutations in well-studied human cancer driver genes. To explore endogenous mutagenesis, we used MEFs ectopically expressing activation-induced cytidine deaminase (AID) and observed an excess of AID signature mutations in immortalised cell lines compared to their non-transgenic counterparts. MEF immortalisation is thus a simple and powerful strategy for modelling cancer mutation landscapes that facilitates the interpretation of human tumour genome-wide sequencing data

Low Resistivity Ohmic Contacts to Moderately Doped N-Gaas With Low Temperature Processing

A low-temperature process for forming ohmic contacts to moderately doped GaAs has been optimized using a PdGe metallization scheme. Minimum specific contact resistivity of 1.5 {times} 10{sup {minus}6} {minus}cm{sup 2} has been obtained with a low anneal temperature of 250 C. Results for optimizing both time and temperature are reported and compared to GeAu n-GaAs contacts. Material compositions was analyzed by x-ray photoelectron spectroscopy and circuit metal interconnect contact resisitivity to the low-temperature processed PdGe contacts is reported. For the lowest temperature anneals considered, excess Ge on the ohmic contact layer is suspected of degrading interconnect metal contacts, while higher temperature anneals permitted interconnect metal formation with negligible contact resistivity. Atomic force microscopy measurements showed that the PdGe surface morphology is much more uniform than standard GeAu contacts

Chromatin remodeling enzyme Brg1 is required for mouse lens fiber cell terminal differentiation and its denucleation

These studies demonstrate a cell-autonomous role for Brg1 in lens fiber cell terminal differentiation and identified DNase IIβ as a potential direct target of SWI/SNF complexes. Brg1 is directly or indirectly involved in processes that degrade lens fiber cell chromatin. The presence of nuclei and other organelles generates scattered light incompatible with the optical requirements for the lens

Equivalencing the Collector System of a Large Wind Power Plant: Preprint

This paper focuses on our effort to develop an equivalent representation of a wind power plant collector system for power system planning studies

Model Validation at the 204-MW New Mexico Wind Energy Center

Poster for WindPower 2006 held June 4-7, 2006, in Pittsburgh, PA, describing model validation at the 204-MW New Mexico Wind Energy Center