The automation of proof: a historical and sociological exploration

This article reviews the history of the use of computers to automate mathematical proofs. It identifies three broad strands of work: automatic theorem proving where the aim is to simulate human processes of deduction; automatic theorem proving where any resemblance to how humans deduce is considered to be irrelevant; and interactive theorem proving, where the proof is directly guided by a human being. The first strand has been underpinned by commitment to the goal of artificial intelligence; practitioners of the second strand have been drawn mainly from mathematical logic; and the third strand has been rooted primarily in the verification of computer programs and hardware designs     

Constraints on human arm movement trajectories.

Analyzed the 3-dimensional arm movement trajectories of 5 right-handed undergraduates under the following conditions: pointing to a target with the index finger vs grasping a target-sized disk, grasping a fragile object vs a soft resilient object, and grasping a disk either to throw into a large box or place into a tight fitting well. Results show that the main factor in the shape of arm trajectories was the point where peak velocity was reached as a function of total movement duration. When task demands required greater precision, the main deceleration phase of the trajectory increased. Results support a view of movement production as relatively specific to the past experience of the performer and the constraints of the task. (French abstract) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Comparison of Techniques for Prediction of Mechanical Strength of Firefighters’ Protective Clothing Using Near-Infrared Spectral Data

Fire Technology - As most textile tests are destructive, non-destructive test (NDT) methods are needed to evaluate in-use firefighters’ protective clothing and to provide guidance as to when...     

Steam oxidation and microstructural evolution of rare earth silicate environmental barrier coatings

A primary failure mode for environmental barrier coatings (EBCs) on SiC ceramic matrix composites (CMCs) is the oxidation of the intermediate Si-bond coating, where the formation of SiO₂ at the bond coating–EBC interface results in debonding and spallation. This work compares the microstructure evolution and steam oxidation kinetics of the Si-bond coating beneath yttrium/ytterbium disilicate ((Y/Yb)DS) and ytterbium disilicate/monosilicate (YbDS/YbMS) EBCs to better understand the impact of EBC composition on oxidation kinetics. After 500 1-h cycles at 1350°C, (Y/Yb)DS displayed a decreasing concentration of the monosilicate minor phase and increasing concentration of porosity as furnace cycling time increased, whereas the YbDS/YbMS EBC displayed negligible microstructural evolution. For both EBC systems, thermally grown oxide growth rates in steam were found to increase by approximately an order magnitude compared to dry air oxidation. The (Y/Yb)DS EBC displayed a reduced steam oxidation rate compared to YbDS/YbMS.     

Katalytische Dechlorierung von Chlorkohlenwasserstoffen aus kontaminierten Grundw?ssern

Im Rahmen des Forschungsverbundes SAFIRA wurden zwei neue Katalysatorsysteme zur reduktiven Dehalogenierung von CKW mit H2 entwickelt und am Standort Bitterfeld in Grundwasser-Durchflussreaktoren untersucht. Die katalytisch aktive Komponente Pd wurde zum Schutz vor Vergiftung durch ionische Verbindungen zum einen in hydrophobe Polymermembranen eingebettet, zum anderen wurden Pd-Cluster in den Poren hydrophober Zeolithe erzeugt. Die erreichten Standzeiten beider Katalysatoren waren trotzdem bedingt durch die Bildung von H ₂ S und organischen Schwefelverbindungen durch mikrobiologische Sulfatreduktion gering. Die Katalysatoren waren zwar durch eine Spülung mit Hypochlorit regenerierbar, unterlagen aber nach wenigen Tagen erneuter Vergiftung. Der Einsatz von Pd-Katalysatoren unter Bitterfelder Grundwasserbedingungen wird deshalb als problematisch eingesch?tzt.     

Beryllium-7 as a tracer of short-term sediment deposition and resuspension in the Fox River, Wisconsin

Short-term (approximately monthly) sediment deposition and resuspension rates of surficial bed sediments in two PCB-laden impoundments on the Fox River, WI, were determined in the summer and fall of 1998 using 7Be, a naturally occurring radioisotope produced in the atmosphere. Decay-corrected activities and inventories of 7Be were measured in bed sediment and in suspended particles. Beryllium-7 activities generally decreased with depth in the top 5-10 cm of sediments and ranged from undetectable to approximately 0.9 pCi cm(-3). Inventories of 7Be, calculated from the sum of activities from all depths, ranged from 0.87 to 3.74 pCi cm(-2), and the values covaried between sites likely reflecting a common atmospheric input signal. Activities of 7Be did not correlate directly with rainfall. Partitioning the 7Be flux into "new" and "residual" components indicated that net deposition was occurring most of the time during the summer. Net erosion, however, was observed at the upstream site from the final collection in the fall. This erosion event was estimated to have removed 0.10 g (cm of sediment)(-2), corresponding to approximately 0.5 cm of sediment depth, and approximately 6-10 kg of polychlorinated biphenyls (PCBs) over the whole deposit. Short-term accumulation rates were up to approximately 130 times higher than the long-term rates calculated from 137Cs profiles, suggesting an extremely dynamic sediment transport environment, even within an impounded river system.     

Evanescent wave cavity ring-down spectroscopy in a thin-layer electrochemical cell

The application of evanescent wave cavity ring-down spectroscopy (EW-CRDS) in monitoring electrogenerated species within a thin-layer electrochemical cell is demonstrated. In the proof-of-concept experiments described, ferricyanide, Fe(CN)6(3-), was produced by the transport-limited oxidation of ferrocyanide, Fe(CN)6(4-), in a thin-layer solution cell (25-250 microm) formed between an electrode and the hypotenuse of a fused-silica prism. The prism constituted one element of a high-finesse optical cavity arranged in a triangular ring geometry with light being totally internally reflected at the silica/solution interface. The cavity was pumped with the output (approximately 417 nm) of a single-mode external cavity diode laser, which was continuously scanned across the cavity modes. The presence of electrogenerated ferricyanide within the resulting evanescent field, beyond the optical interface, was detected by the enhanced loss of light trapped within the cavity, as measured by the characteristic cavity ring down. In this way, the EW-CRDS technique is sensitive to absorption in only the first few hundred nanometers of solution above the silica surface. The cavity ring-down response accompanying both cyclic voltammetric and step potential chronoamperometry experiments at a variety of electrode-surface distances is presented, and the results are shown to be well reproduced in modeling by finite element methods. The studies herein thus provide a foundation for further applications of EW-CRDS combined with electrochemistry.