Tape casting of polysiloxane-derived ceramic with controlled porosity and surface properties

Tape casting has been applied to produce porous hybrid and SiOC ceramic tapes using ceramic precursors and commercially available polysiloxanes as polymeric binders. SiC particles of two different mean sizes (4.5 or 6.5?μm) were used as inert fillers to prevent shrinkage and increase mechanical stability. Macroporosity was adjusted by varying the azodicarbonamide (ADA) content from 0 to 30?wt.%. Decomposition of the polysiloxanes at 600?°C resulted in the generation of micropores with high specific surface area (187–267 m²?g^?1) and a predominant hydrophobic behavior. At 1000?°C mainly meso/macroporosity were observed (SSA: 32–162 m²?g^?1) accompanied by increased hydrophilicity. The influence of ADA content, SiC size, and pyrolysis temperature on open porosity (2.5–37%), average pore size (<0.01–1.76?μm), surface characteristics, and flexural strength (10.5–121?MPa) were investigated. The porous tapes with different surface characteristics and controlled structure are highly promising for applications involving membrane processes, particularly microfiltration systems (0.1–10?μm).     

Rheology of natural fibers thermoplastic compounds: Flow length and fiber distribution

The presented study investigates the flow length and the corresponding fiber content distribution in the injection‐moulded natural fiber reinforced thermoplastics and its relation to fiber type and processing parameters such as injection pressure, temperature, injection rate and mould tempering by increasing die temperature. In this research, polypropylene compounds with nominally 30 wt % hemp and sisal fibers are investigated. The influence of the injection pressure (500 and 1000 bar), melt temperature (180°C, 200°C, and 220°C), and die temperature (23°C and 80°C) on the fiber content distribution all over the sample is investigated. An increasing linear trend of fiber content along the spiral length is observed as an evidence of a fiber/polymer multiflow system. A pattern for fiber content distribution with respect to the fiber length along the injected spiral can be distinguished, where the longer fibers are usually found at the end of the injected part and the shorter fibers remain near mould entrance point. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 39861.     

Neomycin Inhibition of (+)-7-Iso-Jasmonoyl-L-Isoleucine Accumulation and Signaling

The majority of plant defenses against insect herbivores are coordinated by jasmonate (jasmonic acid, JA; (+)-7-iso-jasmonoyl-L-isoleucine, JA-Ile)-dependent signaling cascades. Insect feeding and mimicking herbivory by application of oral secretions (OS) from the insect induced both cytosolic Ca²⁺ and jasmonate-phytohormone elevation in plants. Here it is shown that in Arabidopsis thaliana upon treatment with OS from lepidopteran Spodoptera littoralis larvae, the antibiotic neomycin selectively blocked the accumulation of OS-induced Ca²⁺ elevation and level of the bioactive JA-Ile, in contrast to JA level. Furthermore, neomycin treatment affected the downstream expression of JA-Ile-responsive genes, VSP2 and LOX2, in Arabidopsis. The neomycin-dependent reduced JA-Ile level is partially due to increased CYP94B3 expression and subsequent JA-Ile turn-over to12-hydroxy-JA-Ile. It is neither due to the inhibition of the enzymatic conjugation process nor to substrate availability. Thus, blocking Ca²⁺ elevation specifically controls JA-Ile accumulation and signaling, offering an insight into role of calcium in defense against insect herbivory.     

Hydrogeologische Untersuchungen bei der Anwendung von Monitored Natural Attenuation (MNA) an einem BTEX-kontaminierten Grundwasserleiter

Bei “Monitored Natural Attenuation” (MNA)-Ma?nahmen werden anhand von Felddaten Prognosen zur Schadensentwicklung erstellt. Zur überprüfung der Aussagef?higkeit von Felddaten hinsichtlich MNA wurden an einer Grundwasserkontamination durch BTEX hydrogeologische Untersuchungen durchgeführt. Hierzu wurden Pumpversuchsdaten, geologische Bohrdaten und Niederschlagsdaten berücksichtigt, daneben die zeitliche Entwicklung der Grundwasserst?nde, der Schadstoffgehalte sowie der hydraulischen Gradienten des Grundwassers. Es zeigte sich eine signifikante Abh?ngigkeit der Schadstoffgehalte für BTEX maximal |r|=0,89 von einem bis zu ±1,4m schwankenden Grundwasserstand, der sich unterschiedlich auswirkt: bei hohem Grundwasserstand sind die Schadstoffgehalte in Herdn?he verringert, gleichzeitig erfolgt eine Ausdehnung der Fahne in Abstromrichtung. Die hydraulischen Gradienten schwanken zwischen 1,5‰ und 15,1‰. Im herdnahen Bereich ist bei hohem Grundwasserstand eine Gradientenverflachung, im Abstrom eine Gradientenversteilung festzustellen. Die Richtungen der horizontalen hydraulischen Gradienten variieren von 12° bis 67°. Unter Berücksichtigung dieser Abh?ngigkeiten ist eine differenzierte Betrachtung der Felddaten für eine nachfolgende Auswertung hinsichtlich MNA erforderlich. Die hydrogeologische und die hydraulische Erkundung ist eine wichtige Voraussetzung zum Verst?ndnis der hydrochemischen Prozesse bei NA in kontaminierten Grundwasserleitern. Die Ergebnisse zeigen, dass hydraulische und hydrogeologische Aspekte bei den in den USA gebr?uchlichen Protokollen zur Anwendung von NA eine zu geringe Beachtung finden.     

Formation of alkylated aromatic acids in groundwater by anaerobic degradation of alkylbenzenes

Evidence for the presence of previously unreported alkylated aromatic acids in anaerobic groundwater samples from a jet fuel-contaminated site is presented. The redox conditions are dominated by sulfate reduction. A gas chromatography/mass spectrometry screening showed a composition of aromatic hydrocarbons ranging from BTEX (C(0)-C(2)-substituted benzenes) up to C(7)-benzenes. Known metabolites like methylbenzoates (C(1)-BA), C(2)-BA, C(3)-BA as well as methylbenzylsuccinates (C(1)-BSA) were detected. Additionally, previously unreported metabolites of higher alkylated benzenes have been identified in the extracts: those are C(2)-BSA to C(5)-BSA as well as C(4)-BA to C(6)-BA, which were detected in the microg/l-concentration range. The formation of C(1)- and C(2)-BSA as well as the C(1)- and C(2)-BA can be linked to structurally corresponding parent contaminants like the xylene isomers and the trimethylbenzene isomers. The C(3)-BSA and C(3)-BA represent metabolites of C(4)-benzenes. The occurrence of C(4)-C(5)-BSA and C(4)-C(6)-BA is attributed to C(5)-C(7)-benzenes acting as parent compounds. The concentration of total aromatic contaminants decreased along the plume centre line. In contrast, benzoates and benzylsuccinates (BA and BSA) showed constant concentrations over a distance of 84 m. BA concentrations were up to 162 times higher compared to BSA, as indicated by the ratio f(BA/BSA). A pronounced transient behaviour of BSA or an overall persistent behaviour of BA can explain this. Hence, along the plume centre line, f(BA/BSA) was constant over a distance of 128 m. The degradation products detected in a monitoring well are not necessarily tied to contaminants detected in that well. Therefore, the metabolite plume is partly located in front of the contaminant plume, but does not significantly migrate downstream the plume toe.     

Flow and crystallization of saturated fatty acid methyl esters and their binary mixtures

Demand for biodiesel has increased due to being a more environmentally-friendly fuel. Cold weather operation of biodiesel is challenging due to fatty acid methyl ester (FAME) content in biodiesel. Saturated FAMEs crystallize at relatively high temperatures, increase the viscosity of biodiesel, and can clog fuel lines. Here, several factors altered crystallization temperature (CT) of FAMEs, including composition, shear rate, and cooling rate. The crystallization of pure and binary mixtures of methyl palmitate, methyl myristate, and methyl stearate were studied under shear flow and static conditions. Static phase CTs of pure methyl palmitate, methyl myristate, and methyl stearate were 26, 14, and 35°C, respectively. In binary mixtures, CTs were depressed up to 7°C, which agreed with freezing point depression theory. Increasing shear rate up to 100 s⁻¹ decreased CT by 2°C compared to static conditions. Decreasing cooling rate from 1 to 0.1°C/min increased CT less than 2°C. Overall, FAME composition altered CT more than shear flow or cooling rate for pure and binary mixtures of three FAMEs.     

Incidence of adenoviruses in raw and treated water

Adenoviruses are of major public health importance and are associated with a variety of clinical manifestations, i.e. gastroenteritis, eye infections and respiratory infections. The importance of water in the epidemiology of adenoviruses and the potential health risks constituted by adenoviruses in water sources and supplies are widely recognised. This study was conducted to assess the incidence of human adenoviruses in raw and treated water systems. Various raw and treated water were routinely monitored for the presence of adenoviruses, over a 1-year period (July 2000-June 2001). The supplies were derived from acceptable quality surface water sources using treatment processes, which conform to international standards for the production of safe drinking water. Adenoviruses were detected by firstly amplifying the viruses in cell cultures and then amplifying the extracted nucleic acids of these viruses using molecular techniques (nested PCR). The results indicated human adenoviruses present in 13 (12.75%) of the raw and 9 (4.41%) of the treated water samples tested. The combination of cell culture and nested PCR has proved to be a quick and reliable method for the detection of adenoviruses in water environments.     

添加碳纳米管对选区激光熔化AlSi10Mg合金缺陷的影响

利用选区激光熔化成形技术制备了纯AlSi10Mg合金及碳纳米管(carbon nanotubes,CNTs)-AlSi10Mg复合材料。当添加CNTs含量为0.05%(质量分数)时具有一定增强效果,但随着CNTs添加量增大,复合材料性能却因为缺陷的增加而明显下降。木实验利用纳米CT技术对纯合金及CNTs(0.5%)-AlSi10Mg复合材料进行缺陷的三维重构。结果表明,添加0.5%的CNTs后,成形缺陷体积所占比例由12%增加至46%;气孔型缺陷数量明显增加,并且等效直径相对较大。CNTs在粉体中的团聚及对气体的吸附作用是两种类型缺陷增加的根本原因。     

Relating video game exposure,sensation seeking,aggression and socioeconomic factors to school performance

ABSTRACT

The time displacement hypothesis has been widely used to explain the effects of media use on academic performance. This approach has been criticised for its monocausality and weak explanatory power. Utilising a combination of different theoretical perspectives is better suited than utilising only one. Considering displacement, excitement, attraction and third variable hypothesis, this paper argues that the relation between video game use and school performance is not the same for all types of gamers by considering the influence of socioeconomic, psychological and contextual factors. It investigates how gaming patterns (frequency, time of day) and psychological characteristics (sensation seeking, aggression) are related to academic performance for primary and secondary school students. Five hundred and seven students from five primary and four secondary schools in Singapore participated in a paper-pencil survey. Results showed support for a combination of displacement and third variable hypothesis, as overall time spent on video games was negatively associated with primary school children’s and active gamers’ school performances. There was no significant relationship for secondary school children. For primary school children who play games in the morning and afternoon, video game use was negatively associated with school performance. There was no support for the attraction and excitement hypotheses.