Model-based identification and testing of appropriate strategies to minimize N2O emissions from biofilm deammonification

Based on a one-year pilot plant operation of a two-step biofilm nitritation-anammox pilot plant, N2O mitigation strategies were identified by applying a newly developed biofilm modeling approach. Due to adapted plant operation, the N2O emission could be diminished by 75% (8.8% → 2.3% of NH4-Noxidized_AOB). The results (measurement and simulation) confirm the huge importance of denitrification as an N2O source or N2O sink, depending on the boundary conditions. A significant reduction of N2O emissions could only be achieved with a one-step deammonification system, which is related to low nitrite and HNO2 concentrations. Increased oxygen concentrations in the bulk phase are not related to decreased emissions. N2O formation by ammonium-oxidizing bacteria (AOB) just shifts deeper into the biofilm; zones with low oxygen concentrations are not avoidable in biofilm systems. Low oxygen concentrations in the bulk phase, however, result in a reduction of the total net N2O formation due to increased activity of heterotrophic bacteria directly at the source of N2O formation (outer biofilm layer). For the model-based identification of mitigation strategies, the standard modeling approaches for biofilms were expanded by including the factor-based N2O formation and emission approach. The new model 'Biofilm/N2OISAH' was successfully validated using data from pilot-scale measurement campaigns. Altogether, the investigation confirms that the employed digital model can strongly support the development of N2O mitigation strategies without the need for specialized measurement inside the biofilm

Comparing linkage designs based on land facets to linkage designs based on focal species

Least-cost modeling for focal species is the most widely used method for designing conservation corridors and linkages. However, these designs depend on today's land covers, which will be altered by climate change. We recently proposed an alternative approach based on land facets (recurring landscape units of relatively uniform topography and soils). The rationale is that corridors with high continuity of individual land facets will facilitate movement of species associated with each facet today and in the future. Conservation practitioners might like to know whether a linkage design based on land facets is likely to provide continuity of modeled breeding habitat for species needing connectivity today, and whether a linkage for focal species provides continuity and interspersion of land facets. To address these questions, we compared linkages designed for focal species and land facets in three landscapes in Arizona, USA. We used two variables to measure linkage utility, namely distances between patches of modeled breeding habitat for 5–16 focal species in each linkage, and resistance profiles for focal species and land facets between patches connected by the linkage. Compared to focal species designs, linkage designs based on land facets provided as much or more modeled habitat connectivity for 25 of 28 species-landscape combinations, failing only for the three species with the most narrowly distributed habitat. Compared to land facets designs, focal species linkages provided lower connectivity for about half the land facets in two landscapes. In areas where a focal species approach to linkage design is not possible, our results suggest that conservation practitioners may be able to implement a land facets approach with some confidence that the linkage design would serve most potential focal species. In areas where focal species designs are possible, we recommend using the land facet approach to complement, rather than replace, focal species approaches

Liver X Receptor activation delays chondrocyte hypertrophy during endochondral bone growth

Objective: Activation of the Liver X Receptor (LXR) has recently been identified as a therapeutic strategy for osteoarthritis (OA). Human OA articular cartilage explants show decreased LXR expression, and LXRβ-null mice display OA-like symptoms. LXR agonist administration to OA articular cartilage explants suppresses proteoglycan degradation and restores LXR-activated transcription. We aimed to investigate the effect of LXR activation on chondrocyte differentiation to elucidate the molecular mechanisms behind its protection against OA. Method: The specific LXR agonist, GW3965, was used to examine the effect of LXR activation on chondrocyte differentiation. Tibia organ cultures were used to examine the effect of LXR activation on bone growth and growth plate morphology, followed by immunohistochemical analysis. In ATDC5 and micromass cultures, chondrocyte differentiation was examined through cellular staining and proliferation assays. Various chondrogenic markers were analyzed by real-time reverse-transcription polymerase chain reaction (qRT-PCR) in micromass RNA. Results: Chondrocyte hypertrophy was suppressed by GW3965 treatment, as shown by decreased hypertrophic zone length in the tibial growth plate, decreased alkaline phosphatase staining in ATDC5 and micromass cultures, and down regulation of Col10a1, Mmp13 and Runx2 expression. Increased proliferation in treated ATDC5 cells and up-regulation of Col2a1 expression in treated micromass cultures suggest hypertrophy is suppressed secondary to prolonged proliferation. Decreased p57 levels in treated growth plates suggest this to be due to cell-cycle exit delay. Conclusion: Our findings regarding LXR\u27s role in cartilage development provide insight into how LXR activation prevents cartilage breakdown, further solidifying its potential as a therapeutic target of OA. © 2014 Osteoarthritis Research Society International

Liver X Receptor activation delays chondrocyte hypertrophy during endochondral bone growth

Objective: Activation of the Liver X Receptor (LXR) has recently been identified as a therapeutic strategy for osteoarthritis (OA). Human OA articular cartilage explants show decreased LXR expression, and LXRβ-null mice display OA-like symptoms. LXR agonist administration to OA articular cartilage explants suppresses proteoglycan degradation and restores LXR-activated transcription. We aimed to investigate the effect of LXR activation on chondrocyte differentiation to elucidate the molecular mechanisms behind its protection against OA. Method: The specific LXR agonist, GW3965, was used to examine the effect of LXR activation on chondrocyte differentiation. Tibia organ cultures were used to examine the effect of LXR activation on bone growth and growth plate morphology, followed by immunohistochemical analysis. In ATDC5 and micromass cultures, chondrocyte differentiation was examined through cellular staining and proliferation assays. Various chondrogenic markers were analyzed by real-time reverse-transcription polymerase chain reaction (qRT-PCR) in micromass RNA. Results: Chondrocyte hypertrophy was suppressed by GW3965 treatment, as shown by decreased hypertrophic zone length in the tibial growth plate, decreased alkaline phosphatase staining in ATDC5 and micromass cultures, and down regulation of Col10a1, Mmp13 and Runx2 expression. Increased proliferation in treated ATDC5 cells and up-regulation of Col2a1 expression in treated micromass cultures suggest hypertrophy is suppressed secondary to prolonged proliferation. Decreased p57 levels in treated growth plates suggest this to be due to cell-cycle exit delay. Conclusion: Our findings regarding LXR\u27s role in cartilage development provide insight into how LXR activation prevents cartilage breakdown, further solidifying its potential as a therapeutic target of OA. © 2014 Osteoarthritis Research Society International

International transmission of transitory and persistent monetary shocks under imperfect information

We analyze the transmission of monetary shocks in a new openeconomy macroeconomics model with one-period nominal contracts and imperfect information. Shocks may have transitory and persistent components, which only through accumulation of information over time becomes known. Responses to shocks are altered compared to the case of full information. There are persistent effects on international relative prices, and delayed exchange-rate overshooting is possible following a persistent shock. In some cases, there are (ex post) excess returns as a positive interest rate spread is accompanied by an appreciating currency (or vice versa). Lastly, it is demonstrated that staggering re-inforce persistence

Smoothed Complexity Theory

Smoothed analysis is a new way of analyzing algorithms introduced by Spielman and Teng (J. ACM, 2004). Classical methods like worst-case or average-case analysis have accompanying complexity classes, like P and AvgP, respectively. While worst-case or average-case analysis give us a means to talk about the running time of a particular algorithm, complexity classes allows us to talk about the inherent difficulty of problems. Smoothed analysis is a hybrid of worst-case and average-case analysis and compensates some of their drawbacks. Despite its success for the analysis of single algorithms and problems, there is no embedding of smoothed analysis into computational complexity theory, which is necessary to classify problems according to their intrinsic difficulty. We propose a framework for smoothed complexity theory, define the relevant classes, and prove some first hardness results (of bounded halting and tiling) and tractability results (binary optimization problems, graph coloring, satisfiability). Furthermore, we discuss extensions and shortcomings of our model and relate it to semi-random models.Comment: to be presented at MFCS 201

Model assisted identification of N2O mitigation strategies for full-scale reject water treatment plants

In a 3-year research project, a new approach to forecast biological N2O formation and emission at high-strength reject water treatment has been developed (ASM3/1_N2OISAH). It was calibrated by extensive batch-tests and finally evaluated by long-term measurement campaigns realized at three wastewater treatment plants (WWTPs) with different process configurations for nitrogen removal of reject water. To enable a model application with common full-scale data, the nitritation-connected supplementary processes that are responsible for N2O formation are not depicted in the model. Instead, within the new model approach the N2O formation is linked to the NH4-N oxidation rate by defining specific formation factors [N2O-Nform/NH4-Nox], depending on the concentrations of NO2 and O2 as well as the NH4 load. A comparison between the measured and the modeled N2O concentrations in the liquid and gas phase at the full-scale treatment plants prove the ability of the proposed modelling approach to represent the observed trends of N2O formation, emission and reduction using the standard parameter set of kinetics and formation factors. Thus, enabling a reliable estimation of the N2O emissions for different operational conditions. The measurements indicate that a formation of N2O by AOB cannot completely be avoided. However, a considerable reduction of the formed N2O was observed in an anoxic environment. Applying the model, operational settings and mitigation strategies can now be identified without extensive measurement campaigns. For further enhancement of the model, first results for kinetics of N2O reduction kinetics by denitrification processes were determined in laboratory-scale batch tests

Propagation of nominal shocks in open economies

Empirical evidence documents substantial persistence in the adjustment process to nominal shocks. Existing open-economy models have failed either to generate interesting dynamics or found that the mechanisms are quantitatively weak. We consider the propagation of nominal shocks in a fully specified stochastic intertemporal open-economy model with incomplete capital markets and staggered nominal wage contracts. It is shown that persistence depends on wage-price interdependencies (spiral), which in turn in a general-equilibrium setting depends on structural parameters characterizing both the demand and the supply side of markets. Parameter choices strengthening wage-price interdependencies thus strengthen persistence as is demonstrated analytically and illustrated numerically. A further product of the paper is that it develops a method by which to solve explicitly for a stochastic intertemporal version of the New Open-Economy Macroeconomics model in which the expenditure switching effect is effective

Long-acting β-adrenoceptor agonists in the management of COPD: focus on indacaterol

Bronchodilators are the cornerstone of severe chronic obstructive pulmonary disease (COPD) treatment to improve airflow, symptoms, exercise tolerance, and exacerbations. There is convincing evidence that regular treatment with long-acting bronchodilators is more effective and convenient than treatment with short-acting bronchodilators. Long-acting β-2-agonists include the twice-daily drugs formoterol and salmeterol and, more recently, once-daily indacaterol. Studies with head-to-head comparisons of long-acting bronchodilators are scant, but novel data from controlled trials with the once-daily β(2)-agonist indacaterol indicate superior bronchodilation and clinical efficacy of indacaterol at recommended doses over twice-daily long-acting β(2)-agonists, and at least equipotent bronchodilation compared with once-daily tiotropium. The recent therapeutic developments in COPD underscore a shift from short-acting bronchodilators with multiple dosings per day to reduced dosing frequency and prolonged duration of action, including once-daily treatment, with more consistent effects on various clinical outcomes. This review summarizes relevant clinical data for twice-daily β-2-agonists in COPD, and further focuses on novel data for once-daily indacaterol, including head-to-head comparison trials