Pumping-induced ebullition: a unified and simplified method for measuring multiple dissolved gases

The incorporation of multiple dissolved gas measurements in biogeochemical studies remains a difficult and expensive challenge. Incompatibilities in collection, handling, and storage procedures generally force the application of multiple sampling procedures for multiple gases. This paper introduces the concept and application of pumping-induced ebullition (PIE), a unified approach for routine measurement of multiple dissolved gases in natural waters and establishes a new platform for development of in situ real-time dissolved gas monitoring tools. Ebullition (spontaneous formation of bubbles) is induced by pumping a water sample through a narrow-diametertube (a "restrictor") to decrease hydrostatic pressure (PH) below total dissolved gas pressure (PT). Buoyancy is used to trap bubbles within a collection tower where gas accumulates rapidly (1 mL/min) to support multiple chemical analyses. Providing for field collection of an essentially unlimited and unified volume of gas sample, PIE afforded accurate and precise measurements of major (N2, 02, Ar), trace (CO2, N20, CH4) and ultratrace (CFC11, CFC12, CFC113, SF6) dissolved gases in Wisconsin groundwater, revealing interrelationships between denitrification, apparent recharge age-dates, and historical land use. Compared to conventional approaches, PIE eliminates multiple gas-specific sampling methods, reduces data computations, simplifies laboratory instrumentation, and avoids aqueous production and consumption of biogenic gases during sample storage. A lake depth profile for CO2 demonstrates PIE's flexibility as an in situ real-time platform for dissolved gas measurements. The apparent departures of some gases (SF6, H2, N2O, CO2) from solubility equilibrium behavior warrant further confirmation and theoretical investigation.     

Modified-atmosphere retail packaging of discovery apples

An experimental modified-atmosphere packaging system was used to compare the atmospheric compositions that developed within sealed packs made from a range of films of different permeability properties. The effects of these conditions were then related to the primary quality attributes, i.e. background skin colour and flesh firmness, and the sensory quality of Discovery apples. Concentrations of CO₂ and O₂ within packs were dependent on the permeability of the film and the holding temperature. In packs sealed with low density polyethylene films and held at 20°C, equilibrated atmospheres containing 3-5% CO₂ and 5-6% O₂ developed within 1-2 days. Softening and yellowing of fruit was markedly retarded. In packs sealed with some less permeable films, atmospheres containing 12-20% CO₂ and 0.9-4% O₂ developed within 1-2 days, resulting in retarded softening and yellowing of the fruit but also a high incidence of tainting. Possible commercial applications, benefits and limitations of modified-atmosphere packaging are discussed.     

The one-way quantum computer--a non-network model of quantum computation

A one-way quantum computer (QC _C ) works by performing a sequence of one-qubit measurements on a particular entangled multi-qubit state, the cluster state. No non-local operations are required in the process of computation. Any quantum logic network can be simulated on the QC _C . On the other hand, the network model of quantum computation cannot explain all ways of processing quantum information possible with the QC _C . In this paper, two examples of the non-network character of the QC _C are given. First, circuits in the Clifford group can be performed in a single time step. Second, the QC _C -realization of a particular circuit—the bit-reversal gate—has no network interpretation.     

Computational Modeling of Columnar to Equiaxed Transition in Alloy Solidification

The columnar to equiaxed transition (CET) provides a challenging simulation goal for computational models of alloy solidification, in addition to being an important technological feature of many casting processes. CET thus provides an industrially relevant test‐case for those developing numerical models across a range of scales. Whether or not CET occurs depends on numerous experimental parameters such as cooling rate, speed of columnar growth, thermal gradient in the liquid, and level of grain refiner in the alloy. Information on columnar and equiaxed grain structure, and the transition between the two, is very useful for foundry engineers, at the macroscopic scale of the casting. The detailed microstructure within each grain is determined by typically dendritic growth and local transport of solute and heat. This paper presents a review of recent progress on modeling CET at multiple length scales. It is evident that, whilst micro‐models can provide simulations of physical phenomena, such as the evolution of dendrite morphology, at scales 10^?3 to 10^?5 m, finite computational resources preclude this resolution over the length scale of castings which is in the 10^?2–10⁰ m range. Instead, reasonably accurate models of CET formation in castings can be achieved by meso‐scale modeling featuring 10^?3–10^?2 m phenomena. Such meso‐scale models make use of analytical expressions to simulate dendrite growth in undercooled melts. Recent progress in modeling of CET, at both macro/meso‐ and micro‐scales is reviewed, and computational challenges yet to be met are summarized.     

Mechanical and tribological properties of TiN/Ti multilayer coating

A large area filtered arc deposition (LAFAD) technique was used to deposit TiN/Ti multilayer coatings with fixed TiN layer thickness and different Ti layer thickness. Nanoindention and pin-on-disk tribometer were used to characterize the hardness, elastic modulus, plasticity, friction coefficient, and wear rate of the multilayer coatings. The dependence of the mechanical and tribological properties of the coating on the Ti interlayer thickness was systematically studied. It was found that the increase in the Ti layer thickness resulted in a decrease in the effective hardness and elastic modulus, and an increase in the wear rate, plasticity, and toughness. The coatings with a Ti layer thicknesses of 0, 25 nm and 50 nm possess an excellent combination of high effective hardness (> 20 GPa), high plasticity (> 69%), low friction coefficient, and high wear resistance.     

Performance properties of vertically partitioned object-orientedsystems

A vertically partitioned structure for the design and implementation of object-oriented systems is proposed, and their performance is demonstrated. It is shown that the application-independent portion of the execution overheads in object-oriented systems can be less than the application-independent overheads in conventionally organized systems built on layered structures. Vertical partitioning implements objects through extended type managers. Two key design concepts result in performance improvement: object semantics can be used in the state management functions of an object type and atomicity is maintained at the type manager boundaries providing efficient recovery points. The performance evaluation is based on a case study of a simple but nontrivial distributed real-time system application