The Influence of Model Structure Uncertainty on Water Quality Assessment

Physically-based mathematical water quality models are known as potentially effective tools to simulate the temporal and spatial variations of water quality variables along rivers. Each model relies on specific sets of assumptions and equations to simulate the physico-biochemical processes, which influence on its simulation results. This paper aims to improve the insight in the uncertainties related to state–of–the–art river physico-biochemical water quality modelling. Sensitivity analysis is applied to the processes implemented in three most popular commercial software packages: MIKE11, InfoWorks RS and InfoWorks ICM. This is done for the Molse Neet river case study. Firstly, the physico-biochemical processes are screened to obtain a preliminary assessment on the critical processes and to determine the processes that require more detailed comparison. Then, local sensitivity analysis is carried out to specify the sensitive parameters and processes. Results show that the hydrodynamic results, heat transfer rate and reaeration simulations cause large differences in model simulation outputs for water temperature and dissolved oxygen concentrations. The ignorance of processes related to sediment transport, phytoplankton and bacteria has a significant influence on the higher values of organic matter and lower values of dissolved oxygen concentrations. The three models show consensus on the main pollutant sources explaining organic matter and nitrate concentrations, but disagree on the main factors explaining the DO concentrations.     

Segregation of Pt and Re During CO2 Reforming of CH4

Pt–Re supported on Ce_0.52 Zr_0.48 O₂ was studied for the carbon dioxide reforming of methane at 800 °C. Diffuse reflectance fourier transform infrared spectroscopy and temperature programmed reduction studies suggest that Pt and Re segregation occurs during the reaction. The segregation results in an increase in the Pt sites available for CH₄ decomposition and results in the bimetallic catalyst exhibiting an increase in the conversion of methane with time on stream. After 20 h of reaction, the CH₄ conversion observed for the bimetallic catalyst was the same as the CH₄ conversion observed for the monometallic catalyst.     

Machining and Ceramic/Ceramic Joining to Form Internal Mesoscale Channels

Ceramics and semiconducting materials with internal channels are crucial in a variety of diverse technologies such as "lab on a chip," fuel cell applications, and cooling of microelectronics. In this paper, techniques for fabricating internal channels in brittle materials first are reviewed. Then, the mechanical machining of surface channels in 99.99% pure alumina partially sintered at 600°C and 700°C is discussed. After machining, the partially sintered alumina is sintered to a density of about 97% of theoretical and then joined to 96% pure alumina to convert the surface channels into internal channels.     

Mechanical Properties and Fracture Toughness of α-Al2O3-Platelet-Reinforced Y-PSZ Composites at Room and High Temperatures

YPSZ/Al₂O₃-platelet composites were fabricated by conventional and tape-casting techniques followed by sintering and HIPing. The room-temperature fracture toughness increased, from 4.9 MPa·m^1/2 for YPSZ, to 7.9 MPa·m^1/2 (by the ISB method) for 25 mol% Al₂O₃ platelets with aspect ratio = 12. The room-temperature fiexural strength decreased 21% and 30% (from 935 MPa for YPSZ) for platelet contents of 25 vol% and 40 vol%, respectively. Al₂O₃ platelets improved the high-temperature strength (by 110% over YPSZ with 25 vol% platelets at 800°C and by 40% with 40 vol% platelets at 1300°C) and fracture toughness (by 90% at 800°C and 61% at 1300°C with 40 vol% platelets). An amorphous phase at the Al₂O₃-platelet/YPSZ interface limited mechanical property improvement at 1300°C. The influence of platelet alignment was examined by tape casting and laminating the composites. Platelet alignment improved the sintered density by >1% d _th , high-temperature strength by 11% at 800°C and 16% at 1300°C, and fracture toughness by 33% at 1300°C, over random platelet orientation.     

Eicosapentaenoic and arachidonic acid: Comparison of metabolism and activity in murine epidermal cells

The biological activity, including metabolism and modulation of ornithine decarboxylase activity and DNA synthesis, of arachidonic acid (AA) and eicosapentaenoic acid (EPA) were compared in epidermal cells from SENCAR mice. Radiolabelled AA and EPA were found to be similarly incorporated into and released from membrane phospholipids of unstimulated cultures. However, when cells were stimulated with the tumor promoter 12-0-tetradecanoylphorbol-13-acetate (TPA), the release of AA was significantly higher than the release of EPA. The extent of metabolism of AA and EPA to prostaglandins was determined in both freeze-thawed cell preparations and in viable cultured cells. In the freeze-thawed preparations, use of AA as a substrate resulted in significantly more PGF than when EPA was used as the substrate. However, more PGE₃ was formed than PGE₂. PGD levels were the same for either fatty acid precursor. Prostaglandin production was also determined in viable cultured cells since other influences such as phospholipase A₂ activity can modify prostaglandin production. Control cultures prelabelled with either AA or EPA produced similar amounts of the respective PGF, PGE, and PGD. However, TPA-stimulated cultures produced significantly higher amounts of each prostaglandin in cultures prelabelled with AA compared to cells prelabelled with EPA. HETE or HEPE production was the same both for cultured cells prelabelled with AA or EPA and for homogenates from uncultured cells incubated directly with the radiolabelled fatty acids. TPA-induced ornithine decarboxylase (ODC) was significantly higher in AA-treated cultures compared to EPA-treated cultures. AA supports DNA synthesis to a greater extent than EPA, either alone or in the presence of TPA. These findings suggest that AA and EPA do not have equivalent biological activity in mouse epidermal cells.     

The strength of industrial cokes. 6. Further studies of the influence of coke breeze in a coal charge on tensile strength of coke

The objective of this investigation was to ascertain if there was any pattern in the dependence of the tensile strength of coke on the proportion and particle size of coke-breeze in an oven charge and to establish if it was possible to interpret the changes in tensile strength in terms of coke structural features. Using a small-scale oven in order to obtain the optimum in close control of the charge preparation and carbonization conditions, cokes were prepared from each of two coking coals blended with coke breeze. The tensile strength of these cokes was determined by the diametrical-compression test and some details of their porous nature were determined from density measurements, mercury porosimetry and optical microscopy. The results clearly demonstrate that the tensile strength of coke is, in general, systematically reduced with increasing breeze content of the oven charge, the more coarsely ground breeze leading to a greater reduction of the tensile strength at any level of breeze addition. But very finely ground breeze at relatively low levels of addition can lead to an improvement in the tensile strength. These changes correlate with variations in the apparent density and the total porosity and possibly also with the average pore size.     

Purification and properties of β-amylase produced by bacillus polymyxa

1,4-α-D -glucan maltohydrolase (β-amylase, EC.3.2.1.2.) produced by Bacillus polymyxa was isolated and purified. Some of its properties were examined and compared with those of a typical plant β-amylase. Hydrolysis of periodate oxidised amylose demonstrated an exo mechanism of substrate attack similar to that of sweet potato β-amylase. The effect of sulphydryl reagents on enzyme activity was similar to that reported for plant β-amylases. Consistent with the observation that the enzyme has an exo mechanism of action, it also failed to degrade Schardinger cyclodextrins. These latter compounds acted as inhibitors of the enzyme. The optimum temperature for activity was 37 °C. The enzyme was quite stable at temperatures up to and including 37 °C; 90% of the original activity remained after storage at 37 °C for 6 days. However, the stability decreased rapidly when exposed to temperatures above 37 °C; only 20% of the activity remained after 1 h at 45 °C. The hydrolase exhibited a rather sharp optimum at pH 6.8 for stability at 37 °C. However, the enzyme was quite stable in the pH range 6.4–7.2 at 20 °C but it was shown to be less stable in acidic conditions than the corresponding plant enzymes.     

Validation of the MEDFICTS dietary questionnaire: A clinical tool to assess adherence to American Heart Association dietary fat intake guidelines

Background  

Dietary assessment tools are often too long, difficult to quantify, expensive to process, and largely used for research purposes. A rapid and accurate assessment of dietary fat intake is critically important in clinical decision-making regarding dietary advice for coronary risk reduction. We assessed the validity of the MEDFICTS (MF) questionnaire, a brief instrument developed to assess fat intake according to the American Heart Association (AHA) dietary "steps".     

Variations in diffusion coefficient of disperse dyes in single PET fibres: monitored and interpreted by confocal laser scanning microscopy

A novel method is proposed for determining the diffusion coefficient (D) of disperse dyes in PET fibres. Concentration-distance profiles are recorded on optical sections of single fibres by confocal laser scanning microscopy. This allows for an accurate value of the true diffusion coefficient in the fibres as well as for a founded insight in the dye diffusion process and its interrelation with the glass transition, which is not possible by the commonly used methods. At 130 °C, the common industrial dyeing temperature, the diffusion coefficient showed to be constant for the dyes tested, with D being about five times larger for the anthraquinone dye than for the benzodifuranone dye. At 100-110 °C, near to the start of the glass transition region of the fibres, D could no longer be regarded as a constant for the anthraquinone dye but was concentration dependent. This was explained by the plasticising effect of the anthraquinone dye.