Filterability of activated sludge in membrane bioreactors

The filterability of activated sludge is an important factor for the economical operation of membrane bioreactors (MBR). In the literature mainly investigations on sludge dewaterability in respect to further disposal are published. In this study, a procedure for determining filterability in a crossflow test cell is introduced. Its features are: no increase in sludge concentration during batch trials, crossflow conditions, and little impact on the sludge structure. The activated sludge filterability is given as the ratio of permeate flux after 40 min of operation to clear water flux. Sludge samples of eight different MBR and one conventional wastewater treatment plant (wwtp) have been examined and compared. Contrary to the literature, no impact of suspended solids (SS) concentration, sludge viscosity, or extractable extracellular polymer substances (EPS) concentration on the filterability was found. Instead, the composition of the liquid phase was found to effect most the filterability of activated sludge, a major influence being the concentration of suspended EPS: the higher the suspended EPS concentration, the lower the filtration index. Suspended EPS concentration increases with high mechanical stress in the MBR and high F/M ratios, if the treated wastewater contains considerable amounts of proteins or polysaccharides.     

Poly-ε-caprolactone Coated and Functionalized Porous Titanium and Magnesium Implants for Enhancing Angiogenesis in Critically Sized Bone Defects

For healing of critically sized bone defects, biocompatible and angiogenesis supporting implants are favorable. Murine osteoblasts showed equal proliferation behavior on the polymers poly-ε-caprolactone (PCL) and poly-(3-hydroxybutyrate)/poly-(4-hydroxybutyrate) (P(3HB)/P(4HB)). As vitality was significantly better for PCL, it was chosen as a suitable coating material for further experiments. Titanium implants with 600 µm pore size were evaluated and found to be a good implant material for bone, as primary osteoblasts showed a vitality and proliferation onto the implants comparable to well bottom (WB). Pure porous titanium implants and PCL coated porous titanium implants were compared using Live Cell Imaging (LCI) with Green fluorescent protein (GFP)-osteoblasts. Cell count and cell covered area did not differ between the implants after seven days. To improve ingrowth of blood vessels into porous implants, proangiogenic factors like Vascular Endothelial Growth Factor (VEGF) and High Mobility Group Box 1 (HMGB1) were incorporated into PCL coated, porous titanium and magnesium implants. An angiogenesis assay was performed to establish an in vitro method for evaluating the impact of metallic implants on angiogenesis to reduce and refine animal experiments in future. Incorporated concentrations of proangiogenic factors were probably too low, as they did not lead to any effect. Magnesium implants did not yield evaluable results, as they led to pH increase and subsequent cell death.     

Temporal vertical profiling

Modern systems are enormously complex; many applications today comprise millions of lines of code, make extensive use of software frameworks, and run on complex, multi‐tiered, run‐time systems. Understanding the performance of these applications is challenging because it depends on the interactions between the many software and the hardware components. This paper describes and evaluates an interactive and iterative methodology, temporal vertical profiling, for understanding the performance of applications. There are two key insights behind temporal vertical profiling. First, we need to collect and reason across information from multiple layers of the system before we can understand an application's performance. Second, application performance changes over time and thus we must consider the time‐varying behavior of the application instead of aggregate statistics. We have developed temporal vertical profiling from our own experience of analyzing performance anomalies and have found it very helpful for methodically exploring the space of hardware and software components. By representing an application's behavior as a set of metrics, where each metric is represented as a time series, temporal vertical profiling provides a way to reason about performance across system layers, regardless of their level of abstraction, and independent of their semantics. Temporal vertical profiling provides a methodology to explore a large space of metrics, hundreds of metrics even for small benchmarks, in a systematic way. Copyright © 2010 John Wiley & Sons, Ltd.     

Tripodal polyamines: Adjustable receptors for cation extraction

ABSTRACT

Extraction experiments of a series of tris(2-aminoethyl)amine-based ligands with different aromatic substituents act as efficient extractants for transition metals. Octanol-water distribution measurements, determined stability constants of Ag(I) complexes and Zn(II) extraction studies with different counterions point to the extraction efficiency in dependence of the ligand lipophilicity and the specific structure of the ligand. Competitive extraction experiments showed a selective extraction of Cu(II) from a mixture of Co(II), Ni(II), Cu(II), Zn(II), and Cd(II). Additional hydroxyl groups in (tris(2-hydroxybenzylaminoethyl)amine lead to a loss of this selectivity with extraction yields of 46%, 86% and 97% for Co(II), Ni(II) and Cd(II) ions.     

Hidden Specificities in Enzyme Catalysis: Structural Basis of Substrate Structure-Selectivity Relationship of a Ketoreductase

Enzymes often convert both physiological and non-physiological substrates with high stereoselectivity; yet, for some enzymes, opposite product chirality is observed. A possible explanation is the existence of hidden specificities becoming apparent when non-physiological substrates confer different substrate–enzyme interactions than the physiological substrate. To test this hypothesis, a series of α-methylated β-keto esters were converted with Tyl-KR1, a ketoreductase from polyketide synthesis in Streptomyces fradiae. The conversions of six substrates with different physicochemical properties exhibited enantioselectivities ranging from 84 % ee for R,R to 84 % ee for S,S, yet high and uniform diastereoselectivity (anti, d.r.>9:1). The exchange of a single atom, namely an oxygen ester instead of a thioester, led to almost complete loss of enantioselectivity (<5 % ee). An additional S,S-selective binding mode as a hidden specificity in Tyl-KR1 has been identified through molecular modeling and site-directed mutagenesis.     

Genetically Encoded Biotin Analogues: Incorporation and Application in Bacterial and Mammalian Cells

The biotin–streptavidin interaction is among the strongest known in nature. Herein, the site-directed incorporation of biotin and 2-iminobiotin composed of noncanonical amino acids (ncAAs) into proteins is reported. 2-Iminobiotin lysine was employed for protein purification based on the pH-dependent dissociation constant to streptavidin. By using the high-affinity binding of biotin lysine, the bacterial protein RecA could be specifically isolated and its interaction partners analyzed. Furthermore, the biotinylation approach was successfully transferred to mammalian cells. Stringent control over the biotinylation site and the tunable affinity between ncAAs and streptavidin of the different biotin analogues make this approach an attractive tool for protein interaction studies, protein immobilization, and the generation of well-defined protein–drug conjugates.     

Analysis of Human TAAR8 and Murine Taar8b Mediated Signaling Pathways and Expression Profile

The thyroid hormone derivative 3-iodothyronamine (3-T₁AM) exerts metabolic effects in vivo that contradict known effects of thyroid hormones. 3-T₁AM acts as a trace amine-associated receptor 1 (TAAR1) agonist and activates G_s signaling in vitro. Interestingly, 3-T₁AM-meditated in vivo effects persist in Taar1 knockout-mice indicating that further targets of 3-T₁AM might exist. Here, we investigated another member of the TAAR family, the only scarcely studied mouse and human trace-amine-associated receptor 8 (Taar8b, TAAR8). By RT-qPCR and locked-nucleic-acid (LNA) in situ hybridization, Taar8b expression in different mouse tissues was analyzed. Functionally, we characterized TAAR8 and Taar8b with regard to cell surface expression and signaling via different G-protein-mediated pathways. Cell surface expression was verified by ELISA, and cAMP accumulation was quantified by AlphaScreen for detection of G_s and/or G_i/o signaling. Activation of G-proteins G_q/11 and G_12/13 was analyzed by reporter gene assays. Expression analyses revealed at most marginal Taar8b expression and no gender differences for almost all analyzed tissues. In heart, LNA-in situ hybridization demonstrated the absence of Taar8b expression. We could not identify 3-T₁AM as a ligand for TAAR8 and Taar8b, but both receptors were characterized by a basal G_i/o signaling activity, a so far unknown signaling pathway for TAARs.