Semi‐specific biosensors for measuring BOD in dairy wastewater

BACKGROUND: Semi‐specific microbial biochemical oxygen demand (BOD) biosensors were constructed using living cells of Escherichia coli R17.1.3 (E. coli) and Raoultella terrigena P74.3 (R. terrigena) immobilized in agarose gel matrix. The research involved comparison with the Pseudomonas fluorescens P75 (P. fluorescens) biosensor that had no specificity in decomposing lactose and milk derivates. The constructed BOD biosensors were calibrated with OECD synthetic wastewater and tested with different wastewater samples. RESULTS: The linear range of the calibration curve was 5–200 mg L^?1 BOD₇ for R. terrigena and P. fluorescens based biosensors and 150 mg L^?1 BOD₇ for the E. coli based biosensor. Service life was 60 days for E. coli and P. fluorescens based biosensors and 40 days for R. terrigena based biosensors. BOD values for dairy industry wastewater obtained with current semi‐specific biosensors considerably overestimate BOD₇, while universal biosensors underestimate BOD₇ obtained by the conventional 7‐day BOD test. CONCLUSION: In spite of extensive overestimation of BOD₇ the semi‐specific biosensors enabled better estimation of BOD in dairy industry wastewater than a reference P. fluorescens biosensor. The best result, in terms of service life, stability, sensitivity and reproducibility was accomplished with semi‐specific E.coli biosensor. Copyright © 2010 Society of Chemical Industry     

The occurrence of Campylobacter spp. in Estonian broiler chicken production in 2002–2007

The aim of the present study was to monitor the occurrence of Campylobacter spp. in broiler chicken production in Estonia from 2002 to 2007. Campylobacter spp. was isolated in 163 (12.3%) of 1320 broiler chicken meat samples form 2002 to 2007 and in 115 (6.3%) of 1819 cecal samples in 2005–2007. Campylobacter jejuni was the most commonly isolated species (98.2%), followed by Campylobacter coli (1.4%) and Campylobacter lari (0.4%). The seasonal peak of Campylobacter contamination was from July to September. Our findings showed that Campylobacter contamination at all levels of broiler chicken production in Estonia was low.     

Change is in the wind [From the Editor]

I'm writing this, my first column as the new editor-in-chief, during the final week of the U.S. presidential election campaign. The U.S. citizens are being bombarded by messages from both major candidates talking about change. No matter what they will do, they will change things in Washington. We have all heard that before, but in politics, it seems to be a common topic. When applying for a new job, it is always easy to talk about what one would do to make changes from one's predecessor's activities. The same holds true for the new editor-in-chief.     

Automatic temperature controller for multielement array hyperthermia systems

This paper concerns the optimization and performance analysis of an automatic control algorithm for managing power output of large multielement array hyperthermia applicators. Simulation and corresponding measurement of controller performance in a solid tissue equivalent phantom model is utilized for analysis of controller response to dynamically varying thermal load conditions that simulate clinical treatments. The analysis leads to an optimum controller which demonstrates the ability to achieve a uniform and stable temperature profile over a large surface area regardless of surrounding thermal load. This paper presents several advancements to the performance of a previously published control routine, including: 1) simplified simulation techniques for thorough characterization of controller performance; 2) an optimization procedure leading to an improved hybrid control algorithm for maintaining optimal performance during periods of both "rising" and "steady-state" temperature; 3) performance analysis of a control algorithm tailored for large area hyperthermia treatments with a mulitelement array applicator. The optimized hybrid controller is applied to the conformal microwave array (CMA) hyperthermia system previously developed for heating large area surface disease such as diffuse chestwall recurrence of breast carcinoma, and shown to produce stable, uniform temperatures under the multielement array applicator for all thermal load conditions.     

Theoretical derivation of Darcy's law

Summary Darcy's law for anisotropic porous media is derived from the Navier-Stokes equation by using a formal averaging procedure. Particular emphasis is placed upon the proof that the permeability tensor is symmetric. In addition, it is shown that there is a one-to-one relationship between the local and macroscopic velocity fields. This leads to the interesting phenomenological observation that the local velocity vector at any given point must always lie either on a fixed line or in a fixed plane. All of this holds true for an incompressible homogeneous Newtonian fluid moving slowly through a rigid porous medium with uniform porosity under isothermal and steady state conditions. The question whether Darcy's law is applicable under nonsteady or compressible flow conditions, or when the medium has nonuniform porosity, is also discussed. Finally, it is shown that the Hagen-Poiseuille equation, as well as the expression describing Couette flow between parallel plates, can be derived from the equations presented in this work and may thus be viewed as special cases of Darcy's law.

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Eine theoretische Ableitung des Darcyschen Gesetzes

Zusammenfassung Das Darcysche Gesetz für anisotrope poröse Werkstoffe wird von den Navier-Stokes-Gleichungen durch formale Mittelwertbildung abgeleitet. Insbesondere betont wird der Beweis der Symmetrie des Permeabilitätstensors. Weiter wird gezeigt, daß eine eineindeutige Beziehung zwischen lokalen und makroskopischen Geschwindigkeitsfeldern existiert. Dies führt zur interessanten phänomenologischen Beobachtung, daß in jedem Punkt der lokale Geschwindigkeitsvektor entweder auf einer festen Geraden oder in einer festen Ebene liegt. All dies gilt für inkompressible homogene Newtonsche Flüssigkeiten, die sich langsam, stationär unter isothermen Bedingungen durch einen starren porösen Körper gleichförmiger Porösität bewegen. Die Frage, ob das Darcysche Gesetz für instationäre Strömungen oder kompressible Fälle oder für ungleichförmige Porösität gilt, wird ebenfalls diskutiert. Abschließend wird gezeigt, daß die Hagen-Poiseuille-Gleichung und der Ausdruck für die Couette-Strömung zwischen parallelen Platten von der in dieser Arbeit angegebenen Gleichung abgeleitet und daher als Spezialfälle des Darcyschen Gesetzes betrachtet werden können.

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Nomenclature a scalar ratio betweenv _i and projection of <v _i >^* at centroid ofR in the direction ofv _i - b half distance between parallel plates,L - d diameter of straight tube,L - f any local property of the fluid defined in the pores and vanishing in the solids - <f> bulk-volume average off - <f>^* pore-volume average off - g acceleration due to gravity,LT ^–2 - g _i (0,0,–g),LT ^–2 - G Green's function of porous space - h(f) probability density off on _sf - k _ij permeability tensor,L ² - l _i unit vector lying in the plane ofv _i (orm _i ) and <v _i >^* and perpendicular tom _i - m _i unit vector parallel tov _i - n _i unit vector normal to _sf and pointing into the solids - p local fluid pressure,ML ^–1 T ^–2 - <p>^* macroscopic (pore-volume average) pressure,ML ^–1 T ^–2 - r radius of straight tube,L - R representative elementary volume of porous medium,L ³ - t time,T - v _i local fluid velocity vector,LT ^–1 - <v _i > bulk-volume average ofv _i (darcy velocity or specific flux vector),LT ^–1 - x _i vector of Cartesian coordinates,x ₃ being the vertical,L - _ij –am _i m _j or –( _ij –l _i l _j ) - _m Dirichlet boundary segment of ,L ² - _sf solid-fluid interfaces inR, L ² - ; _ij Kronecker delta - dynamic fluid viscosity,ML ^–1 T ^–1 - fluid density,ML ^–3 - porosity ofR - local force potential, defined as ,L ² T ^–2 - ^* macroscopic (pore-volume average) force potential, defined as ,L ² T ^–2 - _m prescribed values of at external boundaries of porous medium, L²T^–2 - ² Laplacian operator,L ^–2 With 4 Fugures