Growth dynamic of Naegleria fowleri in a microbial freshwater biofilm

The presence of pathogenic free-living amoebae (FLA) such as Naegleria fowleri in freshwater environments is a potential public health risk. Although its occurrence in various water sources has been well reported, its presence and associated factors in biofilm remain unknown. In this study, the density of N. fowleri in biofilms spontaneously growing on glass slides fed by raw freshwater were followed at 32 °C and 42 °C for 45 days. The biofilms were collected with their substrata and characterized for their structure, numbered for their bacterial density, thermophilic free-living amoebae, and pathogenic N. fowleri. The cell density of N. fowleri within the biofilms was significantly affected both by the temperature and the nutrient level (bacteria/amoeba ratio). At 32 °C, the density remained constantly low (1-10 N. fowleri/cm²) indicating that the amoebae were in a survival state, whereas at 42 °C the density reached 30-900 N. fowleri/cm² indicating an active growth phase. The nutrient level, as well, strongly affected the apparent specific growth rate (μ) of N. fowleri in the range of 0.03-0.23 h⁻¹. At 42 °C a hyperbolic relationship was found between μ and the bacteria/amoeba ratio. A ratio of 10⁶ to 10⁷ bacteria/amoeba was needed to approach the apparent μ_max value (0.23 h⁻¹). Data analysis also showed that a threshold for the nutrient level of close to 10⁴ bacteria/amoeba is needed to detect the growth of N. fowleri in freshwater biofilm. This study emphasizes the important role of the temperature and bacteria as prey to promote not only the growth of N. fowleri, but also its survival.     

Long-term stream invertebrate community alterations induced by the insecticide thiacloprid: effect concentrations and recovery dynamics

In pesticide risk assessment, effect concentrations and dynamics of long-term community-level effects caused by pulse exposures remain to be investigated. This is because long-term experiments are exceptionally rare, and most of the previously investigated communities had low proportions of sensitive long-living species. The aim of the present study was to investigate the effect of a single pulse contamination with the insecticide thiacloprid on invertebrates. We employed mesocosms designed to realistically mimic communities in small streams within the agricultural landscape. Specifically, the objectives were to (i) compare the community Lowest-Observed-Effect Concentration (LOEC) with organism-level median lethal concentrations (LC50), and (ii) to assess recovery dynamics with special focus on short- and long-living taxa. The contamination resulted in long-term alteration of the overall invertebrate community structure (7 months, until the end of the experiment). Long-term community LOEC was 3.2 microg/L (Redundancy Analysis), slightly below the acute LC50s known for sensitive invertebrates relevant to the mesocosm community. However, one species (stonefly Nemoura cinerea) was affected at the lowest tested concentration, 70 times below the lowest known LC50. Concerning time to recovery from the effect, we found that the duration depends on the life-cycle characteristics of species, but not on the toxicant concentration: short-living (mulivoltine) species recovered after 10 weeks following contamination, whereas long-living (uni- and semivoltine) species did not recover until the end of the experiment (7 months). The present example shows that concentrations of pesticides at which majority of the species is affected can be predicted by acute organism-level toxicity tests with sensitive species. However, tests with longer observation periods, as well as consideration of environmental factors and inter-taxon variability in sensitivity are required to predict effects on all species comprising a community. Realistic prediction of community recovery dynamics requires consideration of the species' life-cycle traits.     

Laboratory test reactor for the investigation of liquid reducing agents in the selective catalytic reduction of NOx

A test reactor was designed and built for investigating liquid reducing agents in the selective catalytic reduction (SCR) process in the laboratory. The design of the experimental setup is described in detail and its performance was evaluated. Using a glass nebulizer, liquid reducing agents were sprayed directly onto a catalyst positioned in a heated glass reactor with a length of 250 mm and an internal diameter of 20.4 mm or 40 mm. Model exhaust gases were mixed from individual gas components and were heated up to 450?°C in a heat exchanger before entering the reactor. The off-gas was analyzed using two complimentary techniques, a multi-component online FTIR gas analysis and a liquid quench gas absorption setup, to detect higher molecular compounds and aerosols. Due to the versatility of construction, processes not related to SCR, but involving three-phase reactions with gases, liquids and a catalyst, can also be investigated.     

High-resolution microstructural investigations of interfaces between light metal alloy substrates and cold gas-sprayed coatings

Interfaces between light metal alloys, aluminum AA7022, and magnesium AZ91, and optimized cold gassprayed zinc-based coatings are characterized. The analyses include scanning electron microscopy (SEM) as well as transmission electron microscopy (TEM). Investigations by SEM show a seam with intensive mixing of the substrate and coating material, which is indicated by different values of gray due to element contrast. In energy-dispersive spectroscopy analyses, increased zinc concentrations compared with the substrate material are detected in <1 μm thick vortexes inside the seam. The TEM investigations prove that these areas consist of a homogeneous solid solution and submicron-sized or nanosized intermetallic phases with different concentrations of aluminum, zinc, and magnesium. Because diffusion processes cannot result in the observed microstructure. local melting followed by precipitation of intermetallic phases is concluded as the consequence of the intensive mechanical interaction at the substrate-coating interface during particle impact during the cold gas spraying of zinc on magnesium or aluminum substrates. The original version of this paper was published in the CD ROM Thermal Spray Commects: Explore Its Surfacing Potential, International Thermal Spray Conference, sponsored by DVS, ASM International, and HW International Institute of Welding, Basel, Switzerland, May 2–4, 2005, DVS-Verlag GmbH, Düsseldorf, Germany.     

Stability of foams containing proteins, fat particles and nonionic surfactants

The foamability of aqueous suspensions of proteins and fat particles containing different nonionic surfactants relevant to ice cream mix, through which air is continuously bubbled in a foam column, is investigated in terms of the growth of the foam until steady state is reached. Less water-soluble but more oil-soluble Spans 20, 80 and 85 (monolaurate, monooleate and trioleate of Sorbitan) reduced significantly the steady-state foam height and hence the foamability by enhancement of bubble coalescence. In contrast, highly water-soluble Tweens 20 and 80 increased only slightly the steady-state height of the foams as compared to that obtained using surfactant-free suspension. However, moderately water- and oil-soluble Tween 85 (polyoxyethylene sorbitan trioleate) decreased the foamability more significantly than the Spans. The bubbles are found to be small and coalesce relatively fast at the bulk air interface. The bridging of the fat particles by the three oleates could weaken the protein and fat network thereby reducing the elasticity of the air-aqueous phase interface. This is corroborated by the lowest interfacial elasticity measured using a biconical disc oscillatory rheometer. The stability of the foams formed is also determined by measuring the decrease in foam height and increase in mean bubble diameter with time after stopping the air flow. The results are found to verify a published theoretical model, which enabled to determine the parameters controlling foam stability. The Spans reduced the foam stability as the bubbles coalesced rapidly with bulk air. In contrast, the Tweens increased the foam stability as the bubbles coalesced very slowly. The increase of foam stability by Tween 85 under quiescent conditions is consistent with the measured high interfacial shear viscosity.     

变速箱控制单元的创新技术

汽车变速箱市场正在不断地发展中,除了提高产品本身驾驶便利性的吸引力之外,进一步提高燃油效率的期望已成为推动这一市场发展的重要因素。1982年,大陆集团开始生产变速箱控制单元（TCU）,首先用于建议的传统三档变速箱（雷诺）。之后,于1985年用于全轮驱动系统（福特）,1999年用于CVT自动变速箱（奥迪无级变速）,2000年用于卡车变速箱（伊顿）。现在,已用于广泛使用的双离合器变速箱。     

Holographic voltage profiling on 75 nm gate architecture CMOS devices

Voltage profiles of the source-drain region of a CMOS transistor with 75nm gate architecture taken from an off-the-shelf Intel PIII processor are presented. The sample preparation using a dual beam system is discussed as well as details of the electron optical setup of the microscope. Special attention is given to the analysis of the reconstructed holograms.     

Nukleierung und Polymorphie in isotaktischem Polypropylen

Poly(amide acid)s have been synthesized by condensing benzidine-3,3′-dicarboxylic acid (BDC) with various aliphatic diesters EtOOC? R? COOEt with R = (CH₂)_n where n = 2, 4, 5, 6, 7, 8 and R = cis and trans ? CH=CH? , under suitable experimental conditions. These polymers are insoluble in all common organic solvents but are fairly soluble in concentrated sulfuric acid. The polymers were characterized by IR spectral study, viscometric measurements, and thermal analysis.