River water quality model no. 1 (RWQM1): II. Biochemical process equations

In this paper, biochemical process equations are presented as a basis for water quality modelling in rivers under aero-bic and anoxic conditions. These equations are not new, but they summarise parts of the development over the past 75 years. The primary goals of the presentation are to stimulate communication among modellers and field-oriented researchers of river water quality and of wastewater treatment, to facilitate practical application of river water quality modelling, and to encourage the use of elemental mass balances for the derivation of stoichiometric coefficients of biochemical transformation processes. This paper is part of a series of three papers: In the first paper, the general modelling approach is described; in the present paper, the biochemical process equations of a complex model are presented; and in the third paper, recommendations are given for the selection of a reasonable submodel for a specific application

Absolute Frequency Measurements of the Hg^+ and Ca Optical Clock Transitions with a Femtosecond Laser

The frequency comb created by a femtosecond mode-locked laser and a microstructured fiber is used to phase coherently measure the frequencies of both the Hg^+ and Ca optical standards with respect to the SI second as realized at NIST. We find the transition frequencies to be f_Hg=1 064 721 609 899 143(10) Hz and f_Ca=455 986 240 494 158(26) Hz, respectively. In addition to the unprecedented precision demonstrated here, this work is the precursor to all-optical atomic clocks based on the Hg^+ and Ca standards. Furthermore, when combined with previous measurements, we find no time variations of these atomic frequencies within the uncertainties of |(df_Ca/dt)/f_Ca| < 8 x 10^{-14} yr^{-1}, and |(df_Hg/dt)/f_Hg|< 30 x 10^{-14} yr^{-1}.Comment: 6 pages, including 4 figures. RevTex 4. Submitted to Phys. Rev. Let

Rotational Diffusion in a Chain of Particles

We study the coupled rotational diffusion in a two-particle chain on the basis of a Smoluchowski equation and calculate time-correlation functions that are measurable in an experiment. This might be used to explore hydrodynamic interactions in the limit where lubrication theory is valid.Comment: 7 pages, 2 figures, to be published in J. Phys.: Condens. Matte

On the Common Support of Workflow Type and Instance Changes under Correctness Constraints

The capability to rapidly adapt in-progress workflows (WF) is an essential requirement for any workflow system. Adaptations may concern single WF instances or a WF type as a whole. Especially for long-running business processes it is indispensable to propagate WF type changes to in-progress WF instances as well. Very challenging in this context is to correctly adapt a (potentially large) collection of WF instances, which may be in different states and to which various ad-hoc changes may have been previously applied. This paper presents a generic framework for the common support of both WF type and WF instance changes. We establish fundamental correctness principles, position formal theorems, and show how WF instances can be automatically and efficiently migrated to a modified WF schema. The adequate treatment of conflicting WF type and WF instance changes adds to the overall completeness of our approach. By offering more flexibility and adaptability the so promising WF technology will finally deliver

Optimizing tuning masses for helicopter rotor blade vibration reduction including computed airloads and comparison with test data

The development and validation of an optimization procedure to systematically place tuning masses along a rotor blade span to minimize vibratory loads are described. The masses and their corresponding locations are the design variables that are manipulated to reduce the harmonics of hub shear for a four-bladed rotor system without adding a large mass penalty. The procedure incorporates a comprehensive helicopter analysis to calculate the airloads. Predicting changes in airloads due to changes in design variables is an important feature of this research. The procedure was applied to a one-sixth, Mach-scaled rotor blade model to place three masses and then again to place six masses. In both cases the added mass was able to achieve significant reductions in the hub shear. In addition, the procedure was applied to place a single mass of fixed value on a blade model to reduce the hub shear for three flight conditions. The analytical results were compared to experimental data from a wind tunnel test performed in the Langley Transonic Dynamics Tunnel. The correlation of the mass location was good and the trend of the mass location with respect to flight speed was predicted fairly well. However, it was noted that the analysis was not entirely successful at predicting the absolute magnitudes of the fixed system loads

A source of polarized electrons based on photoemission of GaAsP.

The source described is based on photoemission of electrons from 100-GaAs0.62P0.38 activated to negative electron affinity. It is built to inject a beam of polarized electrons into the 350 MeV linear accelerator in Mainz. It is capable of delivering a mean current of 28 μA spin-polarized longitudinally to a degree of 0.44. The lifetime of the cathode under operational conditions is better than 200 h. The source was successfully run in a parity experiment, in which the analysing power of quasielastic scattering from beryllium for longitudinally polarized electrons was measured

Reverberation Mapping and the Physics of Active Galactic Nuclei

Reverberation-mapping campaigns have revolutionized our understanding of AGN. They have allowed the direct determination of the broad-line region size, enabled mapping of the gas distribution around the central black hole, and are starting to resolve the continuum source structure. This review describes the recent and successful campaigns of the International AGN Watch consortium, outlines the theoretical background of reverberation mapping and the calculation of transfer functions, and addresses the fundamental difficulties of such experiments. It shows that such large-scale experiments have resulted in a ``new BLR'' which is considerably different from the one we knew just ten years ago. We discuss in some detail the more important new results, including the luminosity-size-mass relationship for AGN, and suggest ways to proceed in the near future.Comment: Review article to appear in Astronomical Time Series, Proceedings of the Wise Observatory 25th Ann. Symposium. 24 pages including 7 figure

Incorporation of Zn in GaAs during organometallic vapor phase epitaxy growth compared to equilibrium

The zinc concentration measured after organometallic vapor phase epitaxy (GMVPE) growth on (100)-oriented GaAs at 700 °C has been compared to the zinc concentration measured after in-diffusion under near-equilibrium conditions. During diffusion, the concentration of Zn 20 nm below the surface was found to vary with PZn1/2, as expected for bulk solid-vapor equilibrium. During growth, the concentration of Zn varied linearly with PZn up to a maximum value which was found to correspond to the solubility limit set by second phase formation, e.g., growth of Zn3As2. Although large differences were observed between the results of the two experiments when using nominally identical ambient conditions, all of the results are consistent with a thermodynamic model in which the Fermi level at the surface is pinned approximately 200 meV below the intrinsic Fermi level. Typical OMVPE growth conditions appear to give a buIk zinc concentration which is supersaturated relative to the ambient partial pressures used, and to enhance the diffusion of Zn into the substrate

Imaging of cell membrane topography using Tamm plasmon coupled emission

Imaging of the cell membrane topography is important for a clear understanding of various biological activities of cells. We propose a technique for imaging the cell membrane topography that uses a metal-photonic crystal structure instead of a glass-water interface used in conventional polarized total internal reflection fluorescence microscopy (pTIRFM) techniques. Through the metal-photonic crystal of the proposed technique, the fluorophore labels on the cell membrane can be excited by both the p- and s-polarized excitation light, and in each case, the p- and s-polarized radiation from the excited fluorophores can be separated to form an image. We calculate the images of the cell membrane topography that is fusing a granule using the proposed technique and pTIRFM. The image obtained by the proposed technique shows a much greater contrast with respect to the background than that of the image obtained by pTIRFM. We also find that the structural similarity index of the image obtained by the proposed technique to a reference image is ~77%, which is only ~16% for the image obtained by pTIRFM. The proposed technique will help to obtain a clearer and more accurate image of the cell membrane topography, and hence, a deeper understanding of different biological activities