Understanding the detrimental effect of nitrate presence on EBPR systems: effect of the plant configuration

The interaction between enhanced biological phosphorus removal (EPBR) and biological nitrogen removal may result in EBPR failure in full‐scale wastewater treatment plants (WWTPs). This work studies one of the common causes of this failure: the presence of nitrate in the anaerobic phase, which may act as an inhibitor for polyphosphate accumulating organisms (PAO) activity or may activate the competition between PAO and denitrifying bacteria for the carbon source. Several batch experiments were performed with different carbon sources (acetic acid, propionic acid and sucrose) at different nitrate concentrations using PAO‐enriched sludge from two different pilot plants: an anaerobic/aerobic sequential batch reactor (SBR) and an anaerobic/anoxic/aerobic (A²/O) continuous plant. The results imply that the operational conditions of the A²/O pilot plant selected a PAO population capable of i) coexisting with nitrate without an inhibitory effect and ii) outcompeting denitrifying bacteria for the carbon source, in contrast to the SBR pilot plant where nitrate had an inhibitory effect on EBPR. Copyright © 2012 Society of Chemical Industry     

Thermal Diffusivity of La1−x Sr x MnO3 (x < 0.3)

Perovskite manganites are interesting because of their colossal magnetoresistance. In this work high resolution thermal diffusivity measurements of La_1–x Sr _x MnO₃ (0 x 0.3) single crystals in the temperature range from 250 to 400 K are presented. A photopyroelectric device in the standard back configuration has been used. The thermal diffusivity through second-order magnetic phase transitions, as well as through first- and second-order structural phase transitions has been measured. The critical parameters of the sample with x = 0.3 at the ferromagnetic-to-paramagnetic transition have been obtained, and are close to the values predicted by the Ising model.     

Millennium-long damage to building materials in London

Damage functions from a range of sources are used to estimate deterioration of carbonate stone, iron and copper, in addition to the rate of blackening of stone surfaces in London across the period 1100-2100 CE. Meteorological and pollution input is available for only a relatively short part of this span, so non-instrumental weather records and modelled pollution are utilised for historic values, while future climate is adapted from the HadCM3A2 model output and pollution assessed from likely regulatory trends. The results from the different damage functions compare reasonably well showing comparable changes in damage rates with time. A potential square-root dependence of change in deposition velocity of SO₂ to limestone suggests a possible overestimate of damage when pollution is high. Deterioration is especially intense from the 1700s. It is difficult to be certain whether the corrosion of copper accelerated as early as this or it developed in the 20th century. Nevertheless all the functions predict a decline in copper corrosion from the end of the 20th century. A blackening function was developed to relate elemental carbon concentration and the colour of deposited particulate matter to blackening rate, which suggests that soiling was particularly rapid in the late 19th century. The increase and subsequent decrease in damage to building materials is interpreted in terms of a Kuznets curve. The centuries where pollution controlled damage to durable building material seems to be over. Weathering, in a changing climate may have the greatest impact in the future.     

The anti-symmetry principle for quasi-static crack propagation in Mode III

In this note we study a basic propagation criterion for quasi-static crack evolution in Mode III. Using classical techniques of complex analysis, the assumption of stable growth is expressed in terms of the parameters defining the elastic field around the tip. We explore the consequences of the local condition obtained and analyse its role as a crack propagation law. In particular, we herein extend to bounded domains a number of results previously obtained for the whole plane.     

Long‐Term Electrical and Mechanical Function Monitoring of a Human‐on‐a‐Chip System

The goal of human‐on‐a‐chip systems is to capture multiorgan complexity and predict the human response to compounds within physiologically relevant platforms. The generation and characterization of such systems is currently a focal point of research given the long‐standing inadequacies of conventional techniques for predicting human outcome. Functional systems can measure and quantify key cellular mechanisms that correlate with the physiological status of a tissue, and can be used to evaluate therapeutic challenges utilizing many of the same endpoints used in animal experiments or clinical trials. Culturing multiple organ compartments in a platform creates a more physiologic environment (organ–organ communication). Here is reported a human 4‐organ system composed of heart, liver, skeletal muscle, and nervous system modules that maintains cellular viability and function over 28 days in serum‐free conditions using a pumpless system. The integration of noninvasive electrical evaluation of neurons and cardiac cells and mechanical determination of cardiac and skeletal muscle contraction allows the monitoring of cellular function, especially for chronic toxicity studies in vitro. The 28‐day period is the minimum timeframe for animal studies to evaluate repeat dose toxicity. This technology can be a relevant alternative to animal testing by monitoring multiorgan function upon long‐term chemical exposure.     

Controlling carbon microporosity: the structure of carbons obtained from different phenolic resin precursors

Carbons were prepared from resins synthesised using the phenolic precursors phenol, para methylphenol, para ethylphenol, para n-propylphenol, para isopropylphenol and 3,5-dimethylphenol. Loss of phenolic OH from these materials was followed using solid-state nuclear magnetic resonance. The surface areas of the carbons were determined using N₂ and CO₂ adsorption. No significant differences in the loss of phenolic OH were observed. Under the same carbonisation conditions, the para alkyl phenols gave carbons with wide micropores, while the phenol and 3,5-dimethylphenol gave carbons with narrow micropores. Grinding the cured resins prior to carbonisation was found to significantly increase the surface area of the carbons obtained, with the microporous surface area increasing rapidly with a fall in particle size, without a significant increase in burn-off. Higher carbonisation temperatures widened the micropore size distribution, as shown by fitting the CO₂ adsorption isotherm with the Dubinin-Astakhov equation. The ability to change the carbon micropore structure obtained from a simple, well defined precursor, has many potential applications in carbon molecular sieves, catalyst supports and the investigation of adsorption processes.