Retrieval of aerosol properties from combined multiwavelength lidar and sunphotometer measurements

Simulation studies were carried out with regard to the feasibility of using combined observations from sunphotometer (SPM) and lidar for microphysical characterization of aerosol particles, i.e., the retrieval of effective radius, volume, and surface-area concentrations. It was shown that for single, homogeneous aerosol layers, the aerosol parameters can be retrieved with an average accuracy of 30% for a wide range of particle size distributions. Based on the simulations, an instrument combination consisting of a lidar that measures particle backscattering at 355 and 1574 nm, and a SPM that measures at three to four channels in the range from 340 to 1020 nm is a promising tool for aerosol characterization. The inversion algorithm has been tested for a set of experimental data. The comparison with the particle size distribution parameters, measured with in situ instrumentation at the lidar site, showed good agreement.     

Mechanisms of SMP production in membrane bioreactors: Choosing an appropriate mathematical model structure

Being able to predict the soluble microbial product (SMP) concentration, an important foulant in membrane bioreactors (MBRs), with mathematical models provides the opportunity to use foulant production as an MBR design and optimization parameter. This study examined the ability of three mathematical model structures to describe two distinct mechanisms of SMP production. The production mechanisms evaluated are (1) the erosion or hydrolysis of floc-associated extracellular polymeric substance (EPS) and (2) decay of active cells. The models were compared based on their ability to predict SMP concentrations observed in an MBR system during a period of increased SMP and floc-associated EPS production due to increased predation. Predation was an important contributor to overall biomass decay. Short-term batch experiments were also preformed to examine model assumptions related to the (1) production of SMP due to decay of active cells, (2) production of SMP due to erosion of floc-associated EPS, (3) degradability of SMP present in the MBR mixed liquor during increased predation and (4) degradability of eroded floc-associated EPS. Both erosion of floc-associated EPS and decay of active cells were shown to be important independent mechanisms of SMP production. Therefore, a mathematical model used to predict SMP concentrations should provide the ability to capture both mechanisms independently. SMP produced during increased predation were slowly degradable while eroded floc-associated EPS was rapidly degradable. Model results demonstrate that the slowly biodegradable SMP fraction will dominate the bulk phase SMP concentration.     

Predation influences the structure of biofilm developed on ultrafiltration membranes

This study investigates the impact of predation by eukaryotes on the development of specific biofilm structures in gravity-driven dead-end ultrafiltration systems. Filtration systems were operated under ultra-low pressure conditions (65 mbar) without the control of biofilm formation. Three different levels of predation were evaluated: (1) inhibition of eukaryotic organisms, (2) addition of cultured protozoa (Tetrahymena pyriformis), and (3) no modification of microbial community as a control. The system performance was evaluated based on permeate flux and structures of the biofilm. It was found that predation had a significant influence on both the total amount and also the structure of the biofilm. An open and heterogeneous structure developed in systems with predation whereas a flat, compact, and thick structure that homogeneously covered the membrane surface developed in absence of predation. Permeate flux was correlated with the structure of the biofilm with increased fluxes for smaller membrane coverage. Permeate fluxes in the presence or absence of the predators was 10 and 5 L m⁻² h⁻¹, respectively. It was concluded that eukaryotic predation is a key factor influencing the performance of gravity-driven ultrafiltration systems.     

Ansa-Porphyrine mit Alkyl-Kette,Pyridin oder zweitem Porphyrin in der Brücke

Ansa-Porphyrines with an Alkyl Chain, a Pyridine or a Second Porphyrine in the Bridge Porphyrines 1, 2a and 2b with an alkyl chain, a pyridine or an additional porphyrine in the bridge are prepared in yields between 5 and 24% by condensation of appropriate chains 5 and 6 containing two terminal benzaldehyde functions with 3,3′-diethyl-4,4′-dimethyl-2,2'dipyrrylmethane 7 . The synthesis of the dialdehydes 5 and 6 is also described.     

Spektroskopische Untersuchungen an Naphtho[1,2-d]thiazolen. II. Bandenanalyse der Absorptions- und Fluoreszenzspektren von 2-Aryl-naphtho[1,2-d]thiazolen

Spectroscopic Investigations on Naphtho[1.2-d]thiazoles. II. Deconvolution of Absorption and Fluorescence Spectra of 2-Aryl-naphtho[1.2-d]thiazoles Fluorescence measurements were carried out of organic fluorescent compounds of the type of 2-aryl-naphtho[1.2-d]thiazoles ( 1a–k ) substituted in the aryl group by different electronic donor and acceptor substituents. 2-Phenyl-naphtho[1.2-d]thiazole was used in the series of these compounds as the reference system for optical properties. A scheme of vibronic terms in ground and excited states resulting from the spectra of emission, ultraviolet absorption and excitation is given.