Updated Characteristics of Torrential Pools

Power Technology and Engineering - Advanced methods for determining the hydrological and geomorphological characteristics of torrential pools, which are important for the design of reliable and...     

Differentiation of hydroxyproline isomers and isobars in peptides by tandem mass spectrometry

The isomeric 3- and 4-hydroxyprolines are isobaric with the isomers leucine and isoleucine, and all four have, therefore, the same "residue mass" of 113. Secondary fragmentation processes were found that differentiate the hydroxyproline isomers from each other and from the leucines. Variants of synthetic bradykinin containing one or two hydroxyproline moieties were prepared by using manual Edman degradation and/or enzymatic methods. The tandem mass spectra of these peptides were recorded. The C-terminal wn fragment ions allow the differentiation of 4-hydroxyproline from the 3-isomer and isoleucine, while the N-terminal an ions containing 4-hydroxyproline undergo H2O elimination to differentiate this amino acid from the 3-isomer and leucine. Lys-C digestion of a mussel adhesive protein produced a set of decapeptides varying in the degree of hydroxylation of proline and tyrosine. Heterogeneity with respect to 3-hydroxyproline and 4-hydroxyproline at a certain position in these peptides was assessed by tandem mass spectrometry based on the wn ion series in the CID spectra of these Lys-C peptides. Some N-terminal ions further allow for the differentiation of these two isomeric species.     

Pulse chemical vapour infiltration of SiC in porous carbon or SiC participate preform using an r.f. heating system

SiC was infiltrated into a porous carbon or an SiC particulate preform from a gaseous system of 6% CH₃SiCl₃-H₂ using a pulse chemical vapour infiltration apparatus and r.f. heating at 1273 to 1423 K. At 1273 K, the SiC matrix infiltrated the porous carbon initially to half the thickness of the substrate and finally over the full thickness. After 10000 pulses, three-point flexural strength saturated at about 120MPa. SiC particulate preform made from an average particle size of 4m was infiltrated by SiC. After 30000 pulses at 1273 K, the flexural strength of the composite increased to 200 to 220 M Pa.     

Hot corrosion ofα-SiC ceramics by V2O5 melt

The corrosion behaviour of-SiC in V₂O₅ melt has been investigated at elevated temperatures. The corrosion products on the surface of the specimen are removed using HF. The morphologies are also examined. From the observations of bubble formation in the scale and the temperature dependence of the corrosion rate, a kinetic mechanism is proposed. Based on the consistency of the plotted data with the proposed equation and high values of surface reaction rate constant, a diffusion controlling process has been developed.     

Algorithms and complexity concerning the preemptive scheduling of periodic,real-time tasks on one processor

We investigate the preemptive scheduling of periodic, real-time task systems on one processor. First, we show that when all parameters to the system are integers, we may assume without loss of generality that all preemptions occur at integer time values. We then assume, for the remainder of the paper, that all parameters are indeed integers. We then give, as our main lemma, both necessary and sufficient conditions for a task system to be feasible on one processor. Although these conditions cannot, in general, be tested efficiently (unless P=NP), they do allow us to give efficient algorithms for deciding feasibility on one processor for certain types of periodic task systems. For example, we give a pseudo-polynomial-time algorithm for synchronous systems whose densities are bounded by a fixed constant less than 1. This algorithm represents an exponential improvement over the previous best algorithm. We also give a polynomial-time algorithm for systems having a fixed number of distinct types of tasks. Furthermore, we are able to use our main lemma to show that the feasibility problem for task systems on one processor is co-NP-complete in the strong sence. In order to show this last result, we first show the Simultaneous Congruences Problem to be NP-complete in the strong sense. Both of these last two results answer questions that have been open for ten years. We conclude by showing that for incomplete task systems, that is, task systems in which the start times are not specified, the feasibility problem is ₂ ^p -complete.This work was supported in part by National Science Foundation Grant No. CCR-8711579. Some of these results were presented at the 15th Symposium on Mathematical Foundations of Computer Science, 1990.     

Kaolinite-mullite reaction series: a TEM study

The kaolinite-mullite reaction series in single crystal kaolinite has been characterized by transmission electron microscopy. The exotherm observed at 980° C is attributed to the formation of a spinel phase. Mullite crystallites have also been observed with the spinel phase and both phases have a composition near that of 32 mullite. Subsequent heat treatment leads to the growth of mullite crystallites on the original kaolinite plates with the c-axis perpendicular to the plate.     

Computed tomographic imaging of the coronary arterial tree-use of local tomography

It has been demonstrated previously (see E.L. Ritman and A.A. Bove, in State of the Art in Quantitative Coronary Arteriography, p.67-78, 1986) that coronary artery anatomy can be visualized using high-speed, volume-scanning X-ray CT (computed tomography). In the current study it is demonstrated that local image reconstruction (i.e. the reconstruction kernel is ~2(+) mm long), as distinct from more conventional global image reconstruction (i.e. 200(+) mm kernel length), has the advantage of reducing the need for operator interactive image processing. In addition, the local reconstruction algorithm eliminates the need for recording the X-ray projection data over the full transaxial extent of the thorax because it requires only the X-ray attenuation data over the region of the heart. This latter aspect reduces the dynamic range requirements for the sensors and could reduce total X-ray exposure.     

Effect of silver addition on superconductivity in the Bi1.6Pb0.4Sr1.6Ca2Cu3O10−y system

Silver/superconductor composites containing 0 to 80 vol% silver have been prepared and their properties determined. Optimum heat treatment at sintering temperatures ( 800° C) under low oxygen pressures produces material with high critical current density and improves physical properties. Magnetic susceptibility measurements have been found to be consistent with resistivity results. In order to retain a single high-T _c phase with increasing silver content, decreased oxygen partial pressures are required. Using the normal-state resistivity of these composites, a percolation threshold at a silver volume fraction of 43% was observed, while zero resistivity measurements show that a continuous superconducting network can be obtained with up to 80 vol% silver. The critical current density of 21 vol% silver-doped samples was found to be 1520 A cm^–2 at 77.3 K, compared to 260 A cm^–2 for an undoped sample.     

Concurrent reading while writing revisited

A modification is proposed to Peterson's construction of 1-writern-reader multivalued atomic shared variableusingn+2 multivalued safe variables and some boolean atomic variables. The resulting construction is elegant and is simpler than the original one. K. Vidyasankar received B.E. (Elec. Engg.) from Thiagarajar College of Engineering, Madurai, M. Tech. from I.I.T. Kanpur, India, and Ph.D. in Computer Science from University of Waterloo, Canada. He is now an Associate Professor in Computer Science at Memorial University of Newfoundland, Canada. His research interests include concurrency control and recovery in database systems, concurrency in interprocess communication, design and analysis of algorithms, and graph theory.A prelininary version of this paper, under the title Improving Peterson's Construction of 1-Writern-Reader Multivalued Atomic Register, appears in the Proc. 26th Annual Allerton Conference on Communication, Control, and Computing, University of Illinois at Urbana Champaign, September 1988, pp 693–700     

Training for an agricultural discrimination task

Skeleton weed, centaurea juncea, is a declared weed in Western Australia because it competes with grain crops for nutrients and moisture. When it is found during harvesting, mechanised teams search and eradicate it. In an earlier report of field trials (Hartley et al, 1989) it was reported that search teams' detection rate was poor and since search teams had usually never seen skeleton weeds, visual discrimination learning was to be expected and observed during searches. The present study investigated the nature of this discrimination learning in a laboratory by developing a training programme of colour photographic slides of weeds in stubble. Subjects receiving specific training with feedback on their performance compared with those receiving pseudo-training showed a significant improvement in detections. Subsequently the benefit of the programme was validated in a field trial.