Combined biological–chemical (Ozone) treatment of wastewaters containing chloroguaiacols

Biological degradation of chloroguaiacols contained in sulphite pulp chlorine bleaching wastewater was studied in four parallel biological fluidised bed reactor systems—one single aerobic, one single anaerobic and two combined anaerobic–aerobic reactors. At low loading rates, trichloroguaiacols were removed nearly quantitatively. 4,5-Dichloroguaiacol was only partly removed. At high loading rates the anaerobic–aerobic recycle reactor removed individual guaiacols more than the other reactors. Only 4,5,6-trichloroguaiacol was removed best by the anaerobic–aerobic reactors in series. Even mixed culture biofilms adapted during several years of continuous operation did not satisfactorily remove these compounds. Synthetic wastewater, containing chlorinated guaiacols, treated with ozone produced formate and oxalate and quantitatively inorganic chloride. Combined ozonation–biotreatment in two reactors in series as well as in a recycle system allowed complete removal of all individual chlorinated guaiacols (< 1 μmol m^?3 remained). The efficiency of non-purgable organic carbon removal could be increased from ≤0.55 to about 4 mol carbon mol^?1 ozone by combination of ozonation with biotreatment. Simultaneously, the efficiency of removal of chlorinated guaiacols was increased by a factor of 10, which is essential for industrial application.     

Fractionation of potato juice proteins into acid-soluble and acid-coagulable fractions

Potato juice proteins were fractionated by acidification to pH 3 into acid-coagulable and acid-soluble fractions. Both fractions are heterogeneous. They differ in molecular weight, conformation in solution and composition of amino acids. The acid-coagulable fraction consists of units of molecular weight between 32,000 and 87,000, while the acid-soluble fraction consists of units of molecular weight between 17,000 and 27,000. Circular dichroism measurements show that the acid-coagulable fraction is in helical and beta conformations whilst, for the acid-soluble fraction, a substantial contribution of the random conformation is observed. The acid-coagulable fraction has a higher content of methionine than the acid-soluble fraction. It is shown that this type of fractionation is more meaningful than fractionation in terms of albumins and globulins by solubility in water or dilute salt solutions.     

Film and penetration theories for a first-order reaction in exothermic gas absorption

Film and penetration models for simultaneous heat and mass transfer are developed for the absorption of gas with a first-order chemical reaction in the liquid phase with temperature-dependent solubility and reaction rate coefficient. These two models represent two extreme conditions of interfacial temperature rise and gas solubility and they are compared with some previous models (Allan and Mann, 1979; Asai et al., 1985). The approximate analytical expressions of the penetration model of Asai et al. (1985) are in good agreement with the numerical results of this work. The results reveal that under many practical circumstances the gas-liquid interfacial temperature may be several degrees Kelvin higher than the bulk liquid temperature. The degree of deviation of the enhancement factor from its isothermal value at the bulk liquid temperature depends on the degree of difference of a certain dimensionless activation energy group from zero, which confirms the previous finding of Asai et al. (1985).     

Engineering yeast alcohol dehydrogenase. Replacing Trp54 by Leu broadens substrate specificity

Analysis of a crystal structure of alcohol dehydrogenase (Adh)from horse liver suggests that Trp54 in the homologous yeastalcohol dehydrogenase prevents the yeast enzyme from efficientlycatalysing the oxidation of long-chain primary alcohols withbranching at the 4 position (e.g. 4-methyl-1-pentanol, cinnamylalcohol). This residue has been altered to Leu by site-directedmutagenesis. The alteration yields an enzyme that serves asan effective catalyst for both longer straight-chain primaryalcohols and branched chain alcohols.     

Atmospheric spouted bed combustion: The role of hydrodynamics in emissions generation and control

Recent studies have reaffirmed the utility of spouted beds as potential combustion devices for a variety of fuels: solid, liquid and gaseous fuels (Arbib and Levy, 1982; Weinberg et al., 1988; Zhao et al., 1987; Altwicker et al., 1989; Altwicker and Lin, 1991; Altwicker et al., 1993; Konduri et al., 1994). In this study, the role of annulus residence time on the performance of such a spouted bed combustor is investigated. The experiments presented here show that fluid hydrodynamics in the annulus of a spouted bed combustor can significantly influence the overall performance; changing the residence time in the annulus significantly affects the concentrations of products due to incomplete combustion at the exit of the combustor. The annular residence time is varied by changing the shape of the bottom of the reactor, by introducing a draft tube and by changing the bed heighn. Propane is used as the fuel and sand as the bed medium. Inferences from the combustion results are supported by pressure and temperature profiles. A streamtube model (Lim and Mathur, 1976) was used to obtain an estimate of the residence time in the annulus. It is concluded that the flame processes taking place at the top of the annulus play a critical role in the emission generation and that more information is needed to understand the annulus-flame.     

Vergleichende Untersuchung raumakustischer Konzepte von Mehrpersonenbüros hinsichtlich Sprachverständlichkeit,Arbeitsgedächtnisleistung und Arbeitsbehaglichkeit durch Hörversuche

Comparative studies of room‐acoustic concepts for open‐plan offices with regard to speech intelligibility, short‐term memory perfomance and acoustic comfort. Increasing use of tempering the core of reeinforced concrete ceilings of open‐plan offices for cooling and if necessary for heating strongly limits the implementation of sound‐absorbing ceilings. In these cases the classic concept for offices with fully sound‐absorbing ceilings and screen barriers is not applicable anymore. As an alternative to this concept of screen barriers a so‐called partition wall concept is going to be implemented in these open‐plan offices. In this case a sound‐absorbing ceiling is not used anymore; instead room‐high partition walls are mounted, which are highly sound‐absorbing on both sides. The objective of the study was to compare these two concepts for open‐plan offices regarding speech intelligibility on the phone, ability to concentrate and acoustic comfort. In addition to that the effect of low‐frequency absorbers was investigated. To evaluate the acoustic concepts of theses offices audibility tests were conducted. For this purpose the room‐acoustic conditions of the office situations were auralized with the help of measured binaural room impulse responses of original open‐plan offices. For comparison an open‐plan office without room‐acoustic measures was included. With this procedure different office situations are directly comparable.     

Nondeformability of Ventilated and Mortar-Embedded Marble Facade Panels

It is known that in historical buildings as well as new buildings, facade claddings consisting of marble panels, are prone to damage patterns such as softening, crack formation, and bowing. The degree of damage is apparently dependent on the location of the building, the external climatic conditions, and the type of fastening of the facade panels. In this article, it is examined by means of nonstationary thermal simulation, to which extent the temperature fields, which develop in the facade panel, have an effect on the damage of the panel. It is shown that the diurnal and annual amplitude of the panel temperature induced by solar flux, external air temperature fluctuations, and long-wave input radiation and irradiation have a substantial influence on the damage process. On the example of the simulation of the thermal behavior of a facade panel for the building locations in Athens, Greece, Vienna, Austria, and Helsinki, Finland, it is shown that the observed increase of the susceptibility of marble facades to damages can be explained with the increase of the geographical latitude through the differences in the external climatic conditions. It is strongly recommended that architects and restorers install specific marble facade panels (like carrara marble) in close thermal contact with the wall behind, since this reduces the susceptibility of the facade to damage.     

Adhesion Characteristics of PDMS Surfaces During Repeated Pull‐Off Force Measurements

To mimic the adhesive effects of gecko toes, artificial surfaces have been manufactured recently using polydimethylsiloxanes (PDMS). However, the effects of repeated contacts on the adhesive properties remain largely unexplored. In this paper we report on the effect of repeated pull‐off force measurements on the adhesion behavior of PDMS (polymer kit Sylgard 184, Dow Corning) tested with a borosilicate glass probe. A decrease in pull‐off force with increase in number of test cycles is found until a plateau is reached. The initial value and the rate of change in pull‐off force strongly depend on the sample preparation procedure, including curing time and cross‐linking. It is proposed that the behavior is due to steady coverage of the probe with free oligomers. The results are crucial for developing reusable, durable, and residue‐free bioinspired adhesives.     

Functional Adhesive Surfaces with “Gecko” Effect: The Concept of Contact Splitting

Nature has developed reversibly adhesive surfaces whose stickiness has attracted much research attention over the last decade. The central lesson from nature is that “patterned” or “fibrillar” surfaces can produce higher adhesion forces to flat and rough substrates than smooth surfaces. This paper critically examines the principles behind fibrillar adhesion from a contact mechanics perspective, where much progress has been made in recent years. The benefits derived from “contact splitting” into fibrils are separated into extrinsic/intrinsic contributions from fibril deformation, adaptability to rough surfaces, size effects due to surface‐to‐volume ratio, uniformity of stress distribution, and defect‐controlled adhesion. Another section covers essential considerations for reliable and reproducible adhesion testing, where better standardization is still required. It is argued that, in view of the large number of parameters, a thorough understanding of adhesion effects is required to enable the fabrication of reliable adhesive surfaces based on biological examples.     

Failure of fibrous anisotropic materials under combined loading

A failure criterion for anisotropic materials under combined stress is developed and demonstrated. The generality and accuracy of the present theory are illustrated by examination through the use of material systems under various loading conditions. Calculated results are compared with the experimental data throughout four quadrants. It agrees with observation quite well at high values of shear stress, where the Tsai–Hill theory becomes too conservative. The present criterion is also compared with other criteria. The comparison shows that this criterion has a good agreement with the experimental data even when the shear stress component is greater than the shear strength.