Monitoring the abundance and the activity of ammonia-oxidizing bacteria in a full-scale nitrifying activated sludge reactor.

Cell-specific ammonia oxidation rate (AOR) has been suggested to be an indicator of the performance of nitrification reactors and to be used as an operational parameter previously. However, published AOR values change by orders of magnitude and studies investigating full-scale nitrification reactors are limited. Therefore, this study aimed at quantifying ammonia-oxidizing bacteria (AOB) and estimating their in situ cell-specific AOR in a full-scale activated sludge reactor treating combined domestic and industrial wastewaters. Results showed that cell-specific AOR changed between 5.30 and 9.89 fmol cell(-1) h(-1), although no significant variation in AOB cell numbers were obtained (1.54E + 08 ± 0.22 cell/ml). However, ammonia-removal efficiency varied largely (52-79 %) and was proportional to the cell-specific AOR in the reactor. This suggested that the cell-specific AOR might be the factor affecting the biological ammonia-removal efficiency of nitrification reactors independent of the AOB number. Further investigation is needed to establish an empirical relationship to use cell-specific AOR as a parameter to operate full-scale nitrification systems more effectively

Image transmission over fading channels using RS-CC versus LDPC coding

In this paper we present effective means of digital image transmission by means of Forward Error Correcting (FEC) schemes and Orthogonal Frequency Division Multiplexing (OFDM). The transmission was simulated over the AWGN and a Rayleigh fading channel whose power delay profile was adopted from the ITU channel model. The FEC and OFDM parameters were adopted from the DVB-T, WiMAX, and DVB-T2 standards. The results presented herein are in terms of BER, PSNR and visual performances. It is evident from the presented results that effective FEC schemes are necessary for reliable transmission of digital media in a mobile wireless scenario. Image transmission over fading channels using RS-CC versus LDPC coding

Thermodynamic large fluctuations from uniformized dynamics

Large fluctuations have received considerable attention as they encode information on the fine-scale dynamics. Large deviation relations known as fluctuation theorems also capture crucial nonequilibrium thermodynamical properties. Here we report that, using the technique of uniformization, the thermodynamic large deviation functions of continuous-time Markov processes can be obtained from Markov chains evolving in discrete time. This formulation offers new theoretical and numerical approaches to explore large deviation properties. In particular, the time evolution of autonomous and non-autonomous processes can be expressed in terms of a single Poisson rate. In this way the uniformization procedure leads to a simple and efficient way to simulate stochastic trajectories that reproduce the exact fluxes statistics. We illustrate the formalism for the current fluctuations in a stochastic pump model

Do Federal Reserve policy surprises affect the risk perception in the emerging markets?

Employing an event study approach, the present authors analyse whether the Federal Reserve's policy surprises affect the risk perceptions in the emerging markets. Only weak evidence is found when the Federal Reserve follows a more expansionary policy than expected. For all other cases, the policy surprises of the Federal Reserve are ineffective. © 2006 Taylor & Francis

Comparison of Different Methods for the Calculation of the Microvascular Flow Index

The microvascular flow index (MFI) is commonly used to semiquantitatively characterize the velocity of microcirculatory perfusion as absent (0), intermittent (1), sluggish (2), or normal (3). There are three approaches to compute MFI: (1) the average of the predominant flow in each of the four quadrants (MFIby quadrants), (2) the direct assessment during the bedside video acquisition (MFIpoint of care), and (3) the mean value of the MFIs determined in each individual vessel (MFIvessel by vessel). We hypothesized that the agreement between the MFIs is poor and that the MFIvessel by vessel better reflects the microvascular perfusion. For this purpose, we analyzed 100 videos from septic patients. In 25 of them, red blood cell (RBC) velocity was also measured. There were wide 95% limits of agreement between MFIby quadrants and MFIpoint of care (1.46), between MFIby quadrants and MFIvessel by vessel (2.85), and between MFIby point of care and MFIvessel by vessel (2.56). The MFIs significantly correlated with the RBC velocity and with the fraction of perfused small vessels, but MFIvessel by vessel showed the best R2. Although the different methods for the calculation of MFI reflect microvascular perfusion, they are not interchangeable and MFIvessel by vessel might be better

Rapid asssessment of drinking-water quality: a handbook for implementation

The JMP Rapid assessment of drinking-water quality (RADWQ) was conceived by WHO and UNICEF to explore the quality of drinking-water from "improved" sources. Results in five pilot countries showed a wide range of conditions, from full compliance with the WHO Drinking-water Quality Guidelines to specific sources in a given country only meeting standards in 34% of the samples. Further efforts along the lines of RADWQ will take global water quality testing out of the strict sphere of monitoring into the broader field of capacity development. The RADWQ handbook describes the methods and procedures applied by WHO and UNICEF in the five countries, for adoption by any authority or institution that wants to prepare a snapshot of the quality of "improved" sources of drinking-water, as a first step towards strengthening drinking-water quality regulations

Occurrence of periodic Lam\'e functions at bifurcations in chaotic Hamiltonian systems

We investigate cascades of isochronous pitchfork bifurcations of straight-line librating orbits in some two-dimensional Hamiltonian systems with mixed phase space. We show that the new bifurcated orbits, which are responsible for the onset of chaos, are given analytically by the periodic solutions of the Lam\'e equation as classified in 1940 by Ince. In Hamiltonians with C_${2v}$ symmetry, they occur alternatingly as Lam\'e functions of period 2K and 4K, respectively, where 4K is the period of the Jacobi elliptic function appearing in the Lam\'e equation. We also show that the two pairs of orbits created at period-doubling bifurcations of touch-and-go type are given by two different linear combinations of algebraic Lam\'e functions with period 8K.Comment: LaTeX2e, 22 pages, 14 figures. Version 3: final form of paper, accepted by J. Phys. A. Changes in Table 2; new reference [25]; name of bifurcations "touch-and-go" replaced by "island-chain

Differential constraints for the Kaup -- Broer system as a reduction of the 1D Toda lattice

It is shown that some special reduction of infinite 1D Toda lattice gives differential constraints compatible with the Kaup -- Broer system. A family of the travelling wave solutions of the Kaup -- Broer system and its higher version is constructed.Comment: LaTeX, uses IOP styl

Factorization and Lie point symmetries of general Lienard-type equation in the complex plane

We present a variational approach to a general Lienard-type equation in order to linearize it and, as an example, the Van der Pol oscillator is discussed. The new equation which is almost linear is factorized. The point symmetries of the deformed equation are also discussed and the two-dimensional Lie algebraic generators are obtained