Skin-friction measurements in a supersonic combustor with crossflow fuel injection

Shock-tunnel experiments have been performed to measure the effect on skin-friction drag in a supersonic combustor of flow disturbances induced by hydrogen fuel injection transverse to the airstream. Constant-area, circular cross section combustors of lengths varying up to 0.52 m were employed. The experiments were done at a stagnation enthalpy of 7.2 MJ . kg(-1) and a Mach number of 4.3, with a boundary layer that was turbulent downstream of the 0.14-m station in the combustors. Combustor skin-friction drag was measured by a method based on the stress wave force balance, the method being validated by agreement between fuel-off skin-friction drag measurements and predictions using existing skin-friction theories. When fuel was injected, it was found that the drag remained at fuel-off values. Thus, the streamwise vortices and other flow disturbances induced by the fuel injection, mixing, and combustion, which are expected to be present in a scramjet combustor, did not influence the skin-friction drag of the combustors.

Causal and localizable quantum operations

We examine constraints on quantum operations imposed by relativistic causality. A bipartite superoperator is said to be localizable if it can be implemented by two parties (Alice and Bob) who share entanglement but do not communicate, it is causal if the superoperator does not convey information from Alice to Bob or from Bob to Alice. We characterize the general structure of causal complete-measurement superoperators, and exhibit examples that are causal but not localizable. We construct another class of causal bipartite superoperators that are not localizable by invoking bounds on the strength of correlations among the parts of a quantum system. A bipartite superoperator is said to be semilocalizable if it can be implemented with one-way quantum communication from Alice to Bob, and it is semicausal if it conveys no information from Bob to Alice. We show that all semicausal complete-measurement superoperators are semi localizable, and we establish a general criterion for semicausality. In the multipartite case, we observe that a measurement superoperator that projects onto the eigenspaces of a stabilizer code is localizable.

Total chemical synthesis and chemotactic activity of human S100A12 (EN-RAGE)

Human S100A12 (extracellular newly identified RAGE (receptor for advanced glycosylation end products)binding protein), a new member of the S100 family of EF-hand calcium-binding proteins, was chemically synthesised using highly optimised 2-(1H-benzotriazol-1-yl)-1,1,3,3-tetramethyluronium hexafluorophosphate/tert-butoxycarbonyl in situ neutralisation solid-phase chemistry. Circular dichroism studies indicated that CaCl2 decreased the helical content by 27% whereas helicity was marginally increased by ZnCl2. The propensity of S100A12 to dimerise was examined by electrospray ionisation time-of-flight mass spectrometry which clearly demonstrated the prevalence of the non-covalent homodimer (20 890 Da). Importantly, synthetic human S100A12 in the nanomolar range was chemotactic for neutrophils and macrophages in vitro. (C) 2001 Federation of European Biochemical Societies. Published by Elsevier Science B.V. All rights reserved.

Ionic strontium fluorescence as a method for flow tagging velocimetry

A flow tagging technique based upon ionic fluorescence in strontium is investigated for applications to velocity measurements in gas flows. The method is based upon a combination of two laser based spectroscopic techniques, i.e. resonantly-enhanced ionisation and laser-induced ionic fluorescence. Strontium is first ionised and then planar laser-induced fluorescence is utilised to give 2D 'bright images' of the ionised region of the flow at a given time delay. The results show that this method can be used for velocity measurements. The velocities were measured in two types of air-acetylene flames - a slot burner and a circular burner yielding velocities of 5.1 +/- 0.1 m/s and 9.3 +/- 0.2 m/s, respectively. The feasibility of the method for the determination of velocities in faster flows than those investigated here is discussed.

Solution structures by H-1 NMR of the novel cyclic trypsin inhibitor SFTI-1 from sunflower seeds and an acyclic permutant

SFTI-1 is a recently discovered cyclic peptide trypsin inhibitor from sunflower seeds comprising 14 amino acid residues. It is the most potent known Bowman-Birk inhibitor and the only naturally occurring cyclic one. The solution structure of SFTI-1 has been determined by H-1-NMR spectroscopy and compared with a synthetic acyclic permutant. The solution structures of both are remarkably similar. The lowest energy structures from each family of 20 structures of cyclic and acyclic SFTI-1 have an rmsd over the backbone and heavy atoms of 0.29 Angstrom and 0.66 Angstrom, respectively. The structures consist of two short antiparallel beta -strands joined by an extended loop containing the active site at one end. Cyclic SFTI-1 also has a hairpin turn completing the cycle. Both molecules contain particularly stable arrangements of cross-linking hydrogen bonds between the beta -strands and a single disulfide bridge, making them rigid and well defined in solution. These stable arrangements allow both the cyclic and acyclic variants of SFTI-1 to inhibit trypsin with very high potencies (0.5 nM and 12.1 nM, respectively). The cyclic nature of SFTI-1 appears to have evolved to provide higher trypsin inhibition as well as higher stability. The solution structures are similar to the crystal structure of the cyclic inhibitor in complex with trypsin. The lack of a major conformational change upon binding suggests that the structure of SFTI-1 is rigid and already pre-organized for maximal binding due to minimization of entropic losses compared to a more flexible ligand. These properties make SFTI-1 an ideal platform for the design of small peptidic pharmaceuticals or pesticides. (C) 2001 Academic Press.

Asymmetric zonal shim coils for magnetic resonance applications

A method is presented for the systematic design of asymmetric zonal shim coils for magnetic resonance applications. Fourier-series methods are used to represent the magnetic field inside and outside a circular cylinder of length 2L and radius a. The current density on the cylinder is also represented using Fourier series. Any desired field can be specified in advance on the cylinder's radius, over some nonsymmetric portion pL

Replication of bovine papillomavirus type 1 (BPV-1) DNA in Saccharomyces cerevisiae following infection with BPV-1 virions

Saccharomyces cerevisiae protoplasts exposed to bovine papillomavirus type 1 (BPV-1) virions demonstrated uptake of virions on electron microscopy. S. cerevisiae cells looked larger after exposure to BPV-1 virions, and cell wall regeneration was delayed. Southern blot hybridization of Hirt DNA from cells exposed to BPV-1 virions demonstrated BPV-1 DNA, which could be detected over 80 days of culture and at least 13 rounds of division. Two-dimensional gel analysis of Hirt DNA showed replicative intermediates, confirming that the BPV-1 genome was replicating within S. cerevisiae. Nicked circle, linear, and supercoiled BPV-1 DNA species were observed in Hirt DNA preparations from S. cerevisiae cells infected for over 50 days, and restriction digestion showed fragments hybridizing to BPV-1 in accord with the predicted restriction map for circular BPV-1 episomes. These data suggest that BPV-1 can infect S. cerevisiae and that BPV-1 episomes can replicate in the infected S. cerevisiae cells.

Saving, productivity and national income: a discrete-time geometric framework

This paper proposes an alternative geometric framework for analysing the inter-relationship between domestic saving, productivity and income determination in discrete time. The framework provides a means of understanding how low saving economies like the United States sustained high growth rates in the 1990s whereas high saving Japan did not. It also illustrates how the causality between saving and economic activity runs both ways and that discrete changes in national output and income depend on both current and previous accumulation behaviour. The open economy analogue reveals how international capital movements can create external account imbalances that enhance income growth for both borrower and lender economies. (C) 2002 Elsevier Science B.V. All rights reserved.

Analysis of an array of monopoles with the use of a radial waveguide approach

A radial guide field matching method (RGFMM) is used to analyze a circular array antenna consisting of one active monopole surrounded by a concentric array of passive monopoles terminated in arbarary loads. An equivalent admittance matrix for this antenna system is determined to study the input admittance of the active monopole when the peripheral elements are terminated in open or short circuits. RGFMM results are compared with free-space method of moments (FS-MoM) results for a small switched-beam array a seven monopoles. Good agreement is noted. (C) 2002 Wiley Periodicals, Inc.

Investigations into a power-combining structure using a reflect array of dual-feed aperture-coupled microstrip patch antennas

This paper details an investigation of a power combiner that uses a reflect array of dual-feed aperture-coupled microstrip patch antennas and a corporate-fed dual-polarized array as a signal distributing/combining device. In this configuration, elements of the reflect array receive a linearly polarized wave and retransmit it with an orthogonal polarization using variable-length sections of microstrip lines connecting receive and transmit ports. By applying appropriate lengths of these delay lines, the array focuses the transmitted wave onto the feed array. The operation of the combiner is investigated for a small-size circular reflect array for the cases of -3 dB, -6 dB and -10 dB edge illumination by the 2 x 2-element dual-polarized array.

Interference rejection capabilities of different types of array antennas in cellular systems

The suitable use of array antennas in cellular systems results in improvement in the signal-to-interference ratio (StR), This property is the basis for introducing smart or adaptive antenna systems. in general, the SIR depends on the array configuration and is a function of the direction of the desired user and interferers. Here, the SIR performance for linear and circular arrays is analysed and compared.

A monolithic smoothing-gap algorithm for contact-impact based on the signed distance function

A new algorithm has been developed for smoothing the surfaces in finite element formulations of contact-impact. A key feature of this method is that the smoothing is done implicitly by constructing smooth signed distance functions for the bodies. These functions are then employed for the computation of the gap and other variables needed for implementation of contact-impact. The smoothed signed distance functions are constructed by a moving least-squares approximation with a polynomial basis. Results show that when nodes are placed on a surface, the surface can be reproduced with an error of about one per cent or less with either a quadratic or a linear basis. With a quadratic basis, the method exactly reproduces a circle or a sphere even for coarse meshes. Results are presented for contact problems involving the contact of circular bodies. Copyright (C) 2002 John Wiley Sons, Ltd.

Catheter effects in organ perfusion experiments

In a typical isolated organ perfusion experiment, a substance is injected upstream of an organ and then collected at some distance downstream. To reach the organ from the injection site, and then from the organ to the collector, a solute passes through catheters, usually tubes with circular cross-sections. Catheters cause distortion to the concentration-time profile of the perfusion. In this paper, we analyse catheter distribution kinetics from a mathematical point of view, develop the function most suitable for modeling this distribution and successfully apply this function to experimental data. (C) 2002 Academic Press.

Cue competition between elementary trained stimuli: US miscuing, interference, and US omission

The present series of experiments was designed to assess whether rule-based accounts of Pavlovian learning can account for cue competition effects observed after elemental training. All experiments involved initial differential conditioning training with A-US and B alone presentations. Miscuing refers to the fact that responding to A is impaired after one B-US presentation whereas interference is the impairment of responding to A after presentation of C-US pairings. Omission refers to the effects on B of A alone presentations. Experiments 1-2a provided clear evidence for miscuing whereas interference was not found after 1, 5 or 10 C-US pairings. Moreover, Experiments 3 and 3a found only weak evidence for interference in an A-US, B I C-US, D I A design used previously to show the effect. Experiments 4 and 5 failed to find any effect of US omission after one or five omission trials. The present results indicate that miscuing is more robust than is the interference effect. Moreover, the asymmetrical effects of US miscuing and US omission are difficult to accommodate within rule-based accounts of Pavlovian conditioning. (C) 2002 Elsevier Science (USA). All rights reserved.

Characterization of redox centers in dimethyl sulfide dehydrogenase from Rhodovulum sulfidophilum

Dimethyl sulfide dehydrogenase from the purple phototrophic bacterium Rhodovulum sulfidophilum catalyzes the oxidation of dimethyl sulfide to dimethyl sulfoxide. Recent DNA sequence analysis of the ddh operon, encoding dimethyl sulfide dehydrogenase (ddhABC), and biochemical analysis (1) have revealed that it is a member of the DMSO reductase family of molybdenum enzymes and is closely related to respiratory nitrate reductase (NarGHI). Variable temperature X-band EPR spectra (120122 K) of purified heterotrimeric dimethyl sulfide dehydrogenase showed resonances arising from multiple redox centers, Mo(V), [3Fe-4S](+), [4Fe-4S](+), and a b-type heme. A pH-dependent EPR study of the Mo(V) center in (H2O)-H-1 and (H2O)-H-2 revealed the presence of three Mo(V) species in equilibrium, Mo(V)-OH2, Mo(v)-anion, and Mo(V)-OH. Above pH 8.2 the dominant species was Mo(V)-OH. The maximum specific activity occurred at pH 9.27. Comparison of the rhombicity and anisotropy parameters for the Mo(V) species in DMS dehydrogenase with other molybdenum enzymes of the DMSO reductase family showed that it was most similar to the low-pH nitrite spectrum of Escherichia coli nitrate reductase (NarGHI), consistent with previous sequence analysis of DdhA and NarG. A sequence comparison of DdhB and NarH has predicted the presence of four [Fe-S] clusters in DdhB. A [3Fe-4S](+) cluster was identified in dimethyl sulfide dehydrogenase whose properties resembled those of center 2 of NarH. A [4Fe-4S](+) cluster was also identified with unusual spin Hamiltonian parameters, suggesting that one of the iron atoms may have a fifth non-sulfur ligand. The g matrix for this cluster is very similar to that found for the minor conformation of center 1 in NarH [Guigliarelli, B., Asso, M., More, C., Augher, V., Blasco, F., Pommier, J., Giodano, G., and Bertrand, P. (1992) Eur. J. Biochem. 307,63-68]. Analysis of a ddhC mutant showed that this gene encodes the b-type cytochrome in dimethyl sulfide dehydrogenase. Magnetic circular dichroism studies revealed that the axial ligands to the iron in this cytochrome are a histidine and methionine, consistent with predictions from protein sequence analysis. Redox potentiometry showed that the b-type cytochrome has a high midpoint redox potential (E-o = +315 mV, pH 8).