Biofouling und Biokorrosion — die Folgen unerwünschter Biofilme

Microbial layers on interfaces, called “biofilms” are characterized by a polymeric, highly hydrated gel matrix of microbial origin in which the organisms are embedded and immobilized. Biofilms exhibit degradation behaviour different from that free cells and accumulate water, metabolites, and sorbe substances at the interface. They can greatly interfere with technical processes by increasing the fluid friction factor, the hydrodynamic resistance of filter membranes and heat transfer resistance in heat exchanger systems. They can cover surfaces, impart unwanted colour, and contaminate water. Biofilms can attack their support and lead to microbially influenced corrosion (MIC). It is estimated that about 20% to all corrosion damage to metals and building materials is due to microbial influence. Thus, the annual costs of biodeterioration range in billions of dollars. Biofilms play a key role in these processes. They consist of a gel matrix, formed by slime substances, in which the cells are immobilized on the surface of the material. Corrosion is an interfacial process, governed by pH, redox potential, oxygen concentration and other parameters. Biofilms, acting as a transport barrier, may change all these parameters exactly at the site where corrosion takes place compared to the water or air phase surrounding. Thus, a thorough knowledge of the properties and development of biofilms is crucial for the design of effective countermeasures.     

Atomic-scale structure of Mo6S6 nanowires

We have studied the atomic-scale structure of the Mo6S6 nanowires using scanning tunneling microscopy and spectroscopy (STM and STS) and density functional theory (DFT). A novel synthesis route based on metallic Mo precursors is presented for the selective formation of elementary pure Mo6S6 nanowires. The Mo6S6 nanowires selectively organize as trimer bundles, and each of the Mo6S6 nanowires consists of an electrically conducting Mo backbone dressed with a sulfur exterior cap. The Mo6S6 nanowires may thus be of interest as novel building blocks in nanoelectronics because the Mo6S6 nanowires exist in a robust, singular structural conformation with uniquely defined electrical (metallic) properties.     

Interactions between laponite and microbial biofilms in porous media: implications for colloid transport and biofilm stability

Quartz sand columns and sand-filled microscope flow cells were used to investigate the transport characteristics of the clay colloid laponite, and a biofilm-forming bacterium, Pseudomonas aeruginosa SG81. Separate experiments were performed with each particle to determine their individual transport characteristics in clean sand columns. In a second set of experiments, bacterial biofilms were formed prior to introduction of the clay colloids. In the independent transport experiments, bacteria and laponite each conformed to known physicochemical principles. A sodium chloride concentration of 7 x 10(-2) M caused complete retention of the laponite within the sand columns. P. aeruginosa SG81 was generally less influenced by ionic strength effects; it showed relatively low mobility at all ionic strengths tested and some (albeit reduced) mobility when introduced to the columns in 1M NaCl, the highest concentration tested, but nevertheless showed reproducible trends. Under conditions favourable to laponite retention and biofilm stability (7 x 10(-2) MNaCl), laponite suspensions were able to remobilise a portion of the attached bacterial biomass. At low ionic strength, the profile of laponite elution was also altered in the presence of a P. aeruginosa biofilm. These observations suggest that while a reduction in ionic strength has a dominant influence on the mobilisation of biological and inorganic colloids, the presence of laponite and biomass can have a distinct influence on the mobility of both types of colloids. Since these events are likely to occur in subsurface environments, our results suggest that colloid-biofilm interactions will have implications for colloid-bound contaminant transport and the remobilisation of pathogens.     

区域供热系统的运行和维护

区域供热系统的设计、运行和维护的好坏直接影响到供热公司的经济效益和供热系统的使用寿命。本文讨论了区域供热运行管理的技术与管理方面的各种问题，涉及供热的全过程，从热力的生产配送直到与最终用户连接。     

Enhancement of biological activities of nanostructured hydrophobic drug species

We report a study of nanoribbons of quercetin, a phase I clinical trial anticancer drug, and their inhibitory effects on cancer cell proliferation. Novel quercetin nanoribbons have been prepared by atmospheric pressure physical vapor deposition (PVD). The nanostructures have been characterized by optical microscopy, scanning electron microscopy, transmission electron microscopy, and Raman spectroscopy, etc. Significantly enhanced solubility in PBS solution and increased drug release rate have been observed for quercetin nanoribbons in comparison to those of quercetin powder. The observed increase of inhibitory effects of quercetin nanoribbons on 4T1 cancel cell growth is correlated with an improvement in their solubility and drug release behavior.     

Homology Modelling of the GABA Transporter and Analysis of Tiagabine Binding

A homology model of the human GABA transporter (GAT‐1) based on the recently reported crystal structures of the bacterial leucine transporter from Aquifex aeolicus (LeuT) was developed. The stability of the resulting model embedded in a membrane environment was analyzed by extensive molecular dynamics (MD) simulations. Based on docking studies and subsequent MD simulations of three compounds, the endogenous ligand GABA and two potent inhibitors, (R)‐nipecotic acid and the anti‐epilepsy drug tiagabine, various binding modes were identified and are discussed. Whereas GABA and (R)‐nipecotic acid, which are both substrates, are stabilised with residues located deep inside the occluded state binding pocket (including residues Tyr 60 and Ser 396), tiagabine, which contains a large aliphatic side chain, is stabilised in a binding mode that extends from the substrate binding pocket (i.e., stabilised by Phe 294) to the extracellular vestibule, where the side chain is stabilised by aliphatic residues. The tiagabine binding mode, reaching from the substrate binding site to the extracellular vestibule, forces the side chain of Phe 294 to adopt a distinct conformation from that found in the occluded conformation of the transporter. Hence, in presence of tiagabine, GAT‐1 is constrained in an open‐to‐out conformation. Our results may be of particular interest for the design of new GAT‐1 inhibitors.     

Kinetics and thermodynamics of hydrogenation-dehydrogenation for Mg-25%TM (TM = Ti,Nb or V) composites synthesized by reactive ball milling in hydrogen

0.75Mg?0.25TM?H (TM = Ti, Nb or V) samples were mechano-chemically synthesized by reactive ball milling. The detailed reaction mechanism during hydrogen release and uptake was investigated by in-situ synchrotron radiation powder X-ray diffraction (SR-PXD) experiments. The thermodynamic and kinetic properties have been studied by Sievert's method. On the base of calculated values of the Gibbs free energy for reaction of hydrogen absorption (ΔG < 0) it reveals that hydrogenation reaction could thermodynamically proceed at room temperature, which is experimentally confirmed for all of the studied composites. It is clearly shown that β-MgH₂ forms at RT under conditions of experiment. Comparative analysis of the MgTi, MgV and MgNb systems makes it possible to establish that the most effective additive facilitating hydrogen uptake, particularly at RT, is vanadium. It provides the degree of conversion into hydride phase α = 0.86 for the first minute of hydrogenation. In contrast, additives of Nb and Ti provide only α = 0.62 and 0.36, respectively, following the 30 min of exposure. However, this study reveals that for the dehydrogenation process, titanium is the best among the examined additives, which is evidenced by lowest value of activation energy E_a = 53.6 kJ/mol of the hydrogen desorption.