Publications

Use of the Scanning Vibrating Probe for in-Situ Monitoring of SCC Via the Coupling Current in 5000 Series Al Alloys

When as-received or sensitized AA5083 are immersed in an electrolyte, a growing crack creates a galvanic couple with the external surfaces according to the differential aeration hypothesis. Monitoring the resulting “coupling current” yielded “real-time” information about the status of a stress corrosion crack. As a result of this study, we have determined that the scanning vibrating electrode technique (SVET) can be used to monitor the coupling current flowing through the solution from the crack to the external surfaces. Preliminary feasibility studies were performed to map the current/potential in larger galvanic couples designed to simulate Cu-rich intermetallics dispersed in an aluminum matrix. A novel horizontal fracture mechanics apparatus, designed to apply a known stress intensity, was employed to reveal the onset of subcritical crack growth. In addition to the preliminary studies, we successfully designed a setup to allow the typical fracture mechanics testing to occur with the SVET. We report on the progress that was made in designing a customized four-point bend, fracture mechanics device that allows for simultaneous loading and electrochemical mapping. Spatially resolved coupling current/potential maps indicate that both the notch and the crack-tip become and remain anodic for a considerable duration of the crack growth process. Furthermore, there are peaks in the coupling current associated with the onset of subcritical crack growth.

Targeted proteomics for metabolic pathway optimization: Application to terpene production

CCDC 2081075: Experimental Crystal Structure Determination

An entry from the Cambridge Structural Database, the world’s repository for small molecule crystal structures. The entry contains experimental data from a crystal diffraction study. The deposited dataset for this entry is freely available from the CCDC and typically includes 3D coordinates, cell parameters, space group, experimental conditions and quality measures.

The Thermal Pressure and Energy–Volume Coefficients of the Methyl Alcohol – Water and <i>t</i>-Butyl Alcohol – Water Systems

Thermal pressure and energy–volume coefficients have been determined for various methyl alcohol – water and t-butyl alcohol – water mixtures at several temperatures in the range 19–55 °C. The energy–volume coefficient is found to pass through a maximum at 0.3–0.4 mole fraction methyl alcohol and 0.1 mole fraction t-butyl alcohol. This behavior is consistent with the average intermolecular distance passing through a minimum in both systems at the corresponding solvent compositions. The relationship between the energy–volume coefficient, the cohesive energy density, and the structure of aqueous binary systems is examined. The temperature dependence of the thermal pressure coefficient is discussed in terms of the effect of temperature on the susceptibility of the entropy of the two systems to isothermal expansion.

Groundwater dependent ecohydrology in a semi-arid oak savanna (Invited)

Canonical piecewise-linear representation

Every continuous piecewise-linear function of one variable f:R/sup 1/ to R/sup 1/ has a unique canonical piecewise-linear representation. However, only a subclass of higher-dimensional piecewise-linear functions f:R/sup n/ to R/sup n/, n>1, has a canonical piecewise-linear representation. It is proved that the necessary and sufficient conditions for the existence of a canonical piecewise-linear representation is that fpossess a consistent variation property. The geometrical constraints imposed by this property are analyzed and discussed in detail along with many examples.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Mutual Assistance between Federal Reserve Banks, 1913-1960 as Prolegomena to the TARGET2 Debate

This article reconstructs the history of mutual assistance among Federal Reserve Banks. We present data on accommodation operations through which Reserve Banks mutualized gold reserves in emergency situations between 1913 and 1960. Reserve sharing was important in response to liquidity crises and bank runs. Such cooperation was essential for the cohesion of the U.S. monetary union. But fortunes could change, with emergency recipients of gold becoming providers. Because imbalances did not endlessly grow, instead narrowing when region-specific shocks subsided, mutual assistance created only limited tensions. These findings speak to the current debate over TARGET2 balances in Europe.

Synthesis and Reactivity of a Dimeric Ni(I) Methyl Complex

The synthesis and reactivity of a dimeric Ni(I) methyl complex, [(IPr)Ni(μ-CH3)]2, (1; IPr = 1,3-bis(2,6-di-isopropylphenyl)imidazolin-2-ylidene) is reported. Reaction with CO2 results in the formation of a bridging Ni(II) carbonate species. Additionally, 1 activates a variety of element-H bonds to form methane and new Ni-element linkages. In one instance, treatment with SiH4 resulted in Si–H bond activation to form a bridging silylene complex, [(IPr)NiH(μ-SiH2)]2. Finally, complex 1 is a competent catalyst for the coupling of CH3MgCl with aryl halides.

CCDC 1405735: Experimental Crystal Structure Determination

An entry from the Cambridge Structural Database, the world’s repository for small molecule crystal structures. The entry contains experimental data from a crystal diffraction study. The deposited dataset for this entry is freely available from the CCDC and typically includes 3D coordinates, cell parameters, space group, experimental conditions and quality measures.

Atomic-scale observation of the grain-boundary structure of Yb-doped and heat-treated silicon nitride ceramics

The effect of secondary sintering additives and/or a post-sintering heat treatment on the semicrystalline atomic structure of the intergranular phase in silicon nitride ceramics is investigated. Three different Yb-doped Si3N4 ceramic compositions are examined using a scanning transmission electron microscope, whereby the intergranular atomic structure is directly imaged with Ångstrom resolution. The resulting high-resolution images show that the atomic arrangement of the Yb takes very periodic positions along the interface between the intergranular phase and the matrix grains, and that a postsintering 1250°C heat treatment, as well as a change of the secondary sintering additives (Al2O3 vs SiO2), does not alter the atomic positions of Yb. This result has implications for the understanding of how the mechanical properties of ceramics are influenced by the presence of the nanoscale intergranular phase, and for associated computational modeling of its precise role and atomic structure.

Supernovae 2008U, 2008V, and 2008W

Development of Cellulosic Biofuels (PowerPoint)

Adaptive Neuromorphic Architecture (ANA)

A Molecular Surface Functionalization Approach to Tuning Nanoparticle Electrocatalysts for Carbon Dioxide Reduction

Conversion of the greenhouse gas carbon dioxide (CO2) to value-added products is an important challenge for sustainable energy research, and nanomaterials offer a broad class of heterogeneous catalysts for such transformations. Here we report a molecular surface functionalization approach to tuning gold nanoparticle (Au NP) electrocatalysts for reduction of CO2 to CO. The N-heterocyclic (NHC) carbene-functionalized Au NP catalyst exhibits improved faradaic efficiency (FE = 83%) for reduction of CO2 to CO in water at neutral pH at an overpotential of 0.46 V with a 7.6-fold increase in current density compared to that of the parent Au NP (FE = 53%). Tafel plots of the NHC carbene-functionalized Au NP (72 mV/decade) vs parent Au NP (138 mV/decade) systems further show that the molecular ligand influences mechanistic pathways for CO2 reduction. The results establish molecular surface functionalization as a complementary approach to size, shape, composition, and defect control for nanoparticle catalyst design.

CCDC 257950: Experimental Crystal Structure Determination

An entry from the Cambridge Structural Database, the world’s repository for small molecule crystal structures. The entry contains experimental data from a crystal diffraction study. The deposited dataset for this entry is freely available from the CCDC and typically includes 3D coordinates, cell parameters, space group, experimental conditions and quality measures.

The influence of traumatic brain injury on acute stress disorder and post-traumatic stress disorder following motor vehicle accidents

This study compared the acute stress disorder and post-traumatic stress disorder (PTSD) symptom profiles in motor vehicle accident survivors who sustained a mild traumatic brain injury (MTBI) or no TBI. Consecutive adult patients who sustained a MTBI (n = 79) and no TBI (n = 92) were assessed for acute stress disorder within 1 month of their trauma and reassessed for PTSD (MTBI: n = 63; non-TBI; n = 72) 6-months post-trauma. Comparable rates of acute stress disorder and PTSD were reported in MTBI and non-TBI patients. Intrusive memories and fear and helplessness in response to the trauma were reported less frequently by MTBI than non-TBI patients at the acute phase. Six-months post-trauma fewer MTBI patients than non-TBI reported fear and helplessness in response to the trauma. These findings suggest that, whereas impaired consciousness at the time of a trauma may reduce the frequency of traumatic memories in the initial month post-trauma, MTBI does not result in a different profile of longer-term PTSD.

SlowFast Networks for Video Recognition

We present SlowFast networks for video recognition. Our model involves (i) a Slow pathway, operating at low frame rate, to capture spatial semantics, and (ii) a Fast pathway, operating at high frame rate, to capture motion at fine temporal resolution. The Fast pathway can be made very lightweight by reducing its channel capacity, yet can learn useful temporal information for video recognition. Our models achieve strong performance for both action classification and detection in video, and large improvements are pin-pointed as contributions by our SlowFast concept. We report state-of-the-art accuracy on major video recognition benchmarks, Kinetics, Charades and AVA. Code has been made available at: https://github.com/facebookresearch/SlowFast.

On the differential advantages of evergreenness and deciduousness in mediterranean oak woodlands: a flux perspective

We assessed the differential advantages of deciduousness and evergreenness by examining 26 site‐years of carbon dioxide, water vapor, and energy flux measurements from five comparable oak woodlands in France, Italy, Portugal, and California (USA). On average, the evergreen and deciduous oak woodlands assimilated and respired similar amounts of carbon while using similar amounts of water. These results suggest that evergreen and deciduous woodlands have specific, and similar, ecological costs in mediterranean climates, and that both leaf habits are able to meet these costs. What are the mechanisms behind these findings? Deciduous oaks compensated for having a shorter growing season by attaining a greater capacity to assimilate carbon for a given amount of intercepted solar radiation during the well‐watered spring period; at saturating light levels, deciduous oaks gained carbon at six times the rate of evergreen oaks. Otherwise, the two leaf habits experienced similar efficiencies in carbon use (the change in carbon respired per change in carbon assimilated), water use (the change in carbon assimilation per change in water evaporated), and rainfall use (the change in evaporation per change in rainfall). Overall, leaf area index, rather than leaf habit, was the significant factor in determining the absolute magnitude of carbon gained and water lost by each evergreen and deciduous oak woodland over an annual interval; the closed canopies assimilated and respired more carbon and transpired more water than the open canopies. Both deciduous and evergreen mediterranean oaks survive in their seasonally hot/dry, wet/cool native range by ensuring that actual evaporation is less than the supply of water. This feat is accomplished by adjusting the leaf area index to reduce total water loss at the landscape scale, by down‐regulating photosynthesis, respiration, and stomatal conductance with progressive seasonal soil water deficits, and by extending their root systems to tap groundwater.

Photogenerated base in polymer curing & imaging: Radiation-induced crosslinking via a knoevenagel reaction.