Bacteria and fungi in aerosols generated by two different types of wastewater treatment plants

Raw wastewater is a potential carrier of pathogenic microorganisms and may pose a health risk when pathogenic microorganisms become aerosolized during aeration. Two different types of wastewater treatment plants were investigated, and the amounts of cultivable bacteria and fungi were measured in the emitted aerosols. Average concentrations of 17,000 CFU m(-3) of mesophilic, 2,100 CFU m(-3) of TSA-SB bacteria (bacteria associated with certain waterborne virulence factors), 1700 CFU m(-3) of mesophilic and 45 CFU m(-3) of thermotolerant fungi, were found in the aerosol emitted by the aeration tank of the activated sludge plant. In the aerosol of the fixed-film reactor 3000 CFU m(-3) mesophilic and 730CFUm(-3) TSA-SB bacteria, and 180 CFUm(-3) mesophilic and 14 CFU m(-3) thermotolerant fungi were measured. The specific emissions per population equivalent between the two types of treatment plants differed by two orders of magnitude. The microbial flux based on the open water surface area of the two treatment plants was similar. The aerosolization ratios of cultivable bacteria (expressed as CFU m(-3) aerosol/m(-3) wastewater) ranged between 8.4 x 10(-11) and 4.9 x 10(-9). The aerosolization ratio of fungi was one to three orders of magnitude higher and a significant difference between the two types of treatment plants could be observed.     

Three-dimensional materials analysis by confocal Raman microspectroscopy

Two- and three-dimensional spatial analysis of various composite materials was performed with a scanning confocal Raman microspectrometer. Samples include TiO(2) microparticles, mixtures of polymers, and the surface of an older Eprom computer chip. In the last case both structural and compositional information was obtained by means of comparing the signal intensity of the Rayleigh line with that of the silicon Raman line at 520 cm(-1). The spatial compositions of a pain-relief medicine and a pharmaceutical salt mixture could be visualized from characteristic Raman lines of the components.     

Low Temperature Non‐Isothermal Aging of Nitrocellulose

Slow multi‐sample thermal ramp aging experiments were performed on high viscosity lacquer grade nitrocellulose over the temperature range 30–80 °C. Nitrocellulose was used in the fibrous state, in solution and as the gelatinous nitro‐plasticized binder used to bind high explosive crystals (HMX) in a polymer‐bonded explosive (PBX) formulation. Samples were subjected to a slow, stable heating rate (dT/dt) of 10 °C per day with periodic sample withdrawal for analysis by triple detector size exclusion chromatography (SEC). Molecular weight and intrinsic viscosity data indicate inter‐chain recombination/aggregation for fibrous material or highly concentrated solutions, when dry. When in fibrous or gelatinous binder form, little degradation was observed, aside from apparent recombination/aggregation. As a concentrated solution complex behavior was noted; fast eluting peaks formed with increased temperature, accompanied by rapid molecular weight reduction and a marked decrease in light scattering peak area. Progressive dilution of nitrocellulose solutions and/or addition of very small quantities of water reduced the recombination/aggregation effects but did not appear to significantly affect the overall rate of nitrocellulose degradation. Activation energies for nitrocellulose chain scission have been estimated from the molecular weight and intrinsic viscosity data obtained by the thermal ramp method.     

Modelling of SiGe heterobipolar transistors: 200 GHz frequencies with symmetrical delay times

Our basic approach is to develop a symmetrical design with equal delay times for collector, base and the total load to simulate the high frequency behaviour of SiGe heterobipolar transistors (HBTs). On this base we have investigated the feasibility of SiGe HBTs with transit frequencies f_T above 200 GHz. A symmetrical design reaching f_T=208 GHz is presented. The dependence of the high frequency behaviour on Ge content and vertical transistor design is shown. Critical parameters like the maximum current density and the breakthrough voltage are considered. An analytical model is compared to numerical simulations and experimental data.     

Athermal all-polymer arrayed-waveguide grating multiplexer

An athermal arrayed-waveguide grating (AWG) multiplexer relying on an all-polymer approach is reported. The all-polymer AWG consisting of polymer waveguides fabricated on a polymer substrate exhibits excellent performance. By properly adjusting the coefficient of thermal expansion of the polymer substrate, athermal and polarisation-independent AWG devices featuring a wavelength shift of less than ±0.05 nm in the 25-65°C temperature range could be demonstrated     

低成本的冷浆工艺

在室温下,不需烘燥处理的专用浆液可以使经纱的润滑性能提高,冷浆工艺出现在分条整要机上的上蜡机构上,冷浆的投资和运行成本也低于热浆工艺。     

Betoninstandsetzung – quo vadis?

Concrete restoration – quo vadis? This article describes the mechanism of the corrosion process for reinforcing steel in concrete which is not under strain by chlorides. Concluding from that the principles of protection following the guidelines of the German Committee for Reinforced Concrete will be presented. The protection principle “W” will be addressed in particular which simplistically means that thermal insulating measures resp. coatings on concrete surfaces already damaged by corrosion result in a protection against further corrosion. The limits of efficacy of coatings will be referred to.     

Preparation and characterization of novel piezoelectric andpyroelectric polymer electrets

The preparation and characterization of novel piezoelectric and pyroelectric electrets is discussed with respect to their electret properties. Charged heterogeneous electrets, like closed-cell microporous polypropylene (pp) foams and `soft-hard' fluoropolymer hybrids are shown to yield large quasi-static and dynamic piezoelectric responses, indistinguishable from true piezoelectricity. Piezoelectric coefficients comparable to that of ceramic counterparts have been achieved. For the investigation of the piezoelectric and pyroelectric properties of the electret materials, the thermal-pulse technique has been extended towards temperature-dependent investigations and measurements on planar, cylindrical or spherical samples. The potential of the thermal-pulse technique not only for the measurement of electric-field and polarization distributions, but also for acoustical, electromechanical and pyroelectric properties is outlined