Textural changes in metallurgical coke prepared with polyethylene

The effect of high-density polyethylene （HDPE） on the textural features of experimental coke was investigated using polar- ized-light optical microscopy and wavelet-based image analysis. Metallurgical coke samples were prepared in a laboratory-scale furnace with 2.5%, 5.0%, 7.5%, 10.0%, and 12.5% HDPE by mass, and one sample was prepared by 100% coal. The amounts and distribution of textures （isotropic, mosaic and banded） and por~s were obtained. The calculations reveal that the addition of HDPE results in a decrease of mosaic texture and an increase of isotropic texture. Ethylene formed from the decomposition of HDPE is considered as a probable reason for the texture modifications. The approach used in this study can be applied to indirect evaluation for the reactivity and strength of coke.     

Comparative experimental study of sand and binder for flowability and casting mold quality

A good sand mold is an indispensable prerequisite to obtaining a good metal casting. Although sand casting is one of the oldest metal forming technique known to humans, it still has a lot to discover. In a bid to meet the ever-growing demand for quality, economics and increasing environmental restrictions, research is still ongoing to optimize for example the process of making the sand mold. This paper presents a comparative study of six different foundry sands for flowability using simple inexpensive apparatus and some quality parameters achieved by these sands when used with three different types of binder, two organic and one inorganic. The study aims to facilitate the choice of mold materials with a more extensive outlook into their characteristics through a serious of sand and mold tests. A good comparison of already existing materials provides a good reference point when novel materials are investigated. All the sands exhibited ‘good’ flow property according to the simple flowability tests done. However, not the same consensus for flowability rank is reached by all the flow tests. The mold quality tests reveal the strength, loss on ignition and permeability values achieved with each of the binder and sand combination which can also be used in mold material selection.     

The influence of dynamic ice formation on hydraulic heterogeneity in steep streams

During winter, different types of ice formation are commonly observed in northern boreal stream systems. Although largely overlooked today, river ice has profound effects on in‐stream hydraulics and therefore ice processes should be considered in freshwater stream management and assessment. In particular, limited knowledge exists about the impacts of dynamic ice formation on stream environments. Results presented from the changes of in‐stream heterogeneity in three steep stream environments caused by dynamic ice formation demonstrate that the formation of anchor ice and anchor ice dams may induce significant backwater effects by increasing wetted areas (maximum 43%) and water depths (maximum 241%) and reducing water velocities (maximum 70%); independent of minimal changes in discharge. Consequently, stream environments are transformed from fast‐flow to slow‐flow areas, even on a short temporal scale (<12 h). Furthermore, the anchor ice build‐up initiated static (surface) ice formation due to reduced local water velocities upstream ice dams. Thus, dynamic ice formation plays a key role in the balanced ice regime in steep stream environments and contributes largely to stable static ice cover in these environments. Observations from the present study suggest that the current paradigm emphasizing the role of discharge as the main controller of in‐stream heterogeneity may call for a modification in steep streams that experience seasonal ice formation. This is particularly important if future hydraulic‐/habitat models and assessment tools are to be implemented in freshwater management to realistically characterize steep stream environments in cold climate regions on a seasonal scale. Copyright © 2009 John Wiley & Sons, Ltd.     

Microwave absorption properties of pyrolytic carbon nanofilm

We analyzed the electromagnetic (EM) shielding effectiveness in the Ka band (26 to 37 GHz) of highly amorphous nanometrically thin pyrolytic carbon (PyC) films with lateral dimensions of 7.2 × 3.4 mm², which consists of randomly oriented and intertwined graphene flakes with a typical size of a few nanometers. We discovered that the manufactured PyC films, whose thickness is thousand times less than the skin depth of conventional metals, provide a reasonably high EM attenuation. The latter is caused by absorption losses that can be as high as 38% to 20% in the microwave frequency range. Being semi-transparent in visible and infrared spectral ranges and highly conductive at room temperature, PyC films emerge as a promising material for manufacturing ultrathin microwave (e.g., K_a band) filters and shields.     

Tracking the Aquatic Impacts of a Historical Metal Mine Using Lacustrine Protists and Diatom Algae

Two lake sediment cores collected near a closed Cu–Au mine were analyzed for testate amoebas, diatoms, and geochemistry to compare their utility for assessment and monitoring of aquatic impacts of metal mines. Geochemical profiles displayed the mine history as increases in mineral matter-related elements during the mining period, and as post-mining metal peaks. Biotic assemblages co-varied with geochemical shifts, and the most notable ecological changes coincided with the peaks in metal concentrations. Additionally, nutrient enrichment caused a major shift in biotic assemblages. According to the results, the mine affected the lake environment over a relatively large area but the changes were transient. Major ecological effects occurred only after the actual mining period as the tailings weathered, which delayed the metal release. This suggests that mine impacts can be significantly reduced by careful design and after-care of the waste facilities.     

Strong coupling between surface plasmon polaritons and Sulforhodamine 101 dye

We demonstrate a strong coupling between surface plasmon polaritons and Sulforhodamine 101 dye molecules. Dispersion curves for surface plasmon polaritons on samples with a thin layer of silver covered with Sulforhodamine 101 molecules embedded in SU-8 polymer are obtained experimentally by reflectometry measurements and compared to the dispersion of samples without molecules. Clear Rabi splittings, with energies up to 360 and 190 meV, are observed at the positions of the dye absorption maxima. The split energies are dependent on the number of Sulforhodamine 101 molecules involved in the coupling process. Transfer matrix and coupled oscillator methods are used to model the studied multilayer structures with a great agreement with the experiments. Detection of the scattered radiation after the propagation provides another way to obtain the dispersion relation of the surface plasmon polaritons and, thus, provides insight into dynamics of the surface plasmon polariton/dye interaction, beyond the refrectometry measurements.PACS: 42.50.Hz, 33.80.-b, 78.67.-n     

Functionalization of polypropylene with oxazoline and reactive blending of PP with PBT in a corotating twin-screw extruder

The aim of this study was to prepare a compatibilized PP/PBT blend in a twin-screw extruder, using oxazoline-functionalized PP. First we prepared the functionalized PP (PP-g-OXA), and then we used it as a compatibilizer in the subsequent reactive blending stage. Polypropylene was successfully functionalized by ricinoloxazoline maleinate in a corotating twin-screw extruder using a melt free radical grafting technique. Grafting yields up to 2.1 phr were achieved. This functionalized PP used as a compatibilizer markedly improved the mechanical properties of the uncompatibilized PP/PBT (PBT content 30 wt %) blend. Significant improvements were observed, especially in impact strength (Charpy) and elongation at break of the compatibilized blends. The increased interactions between the phases were characterized by SEM analysis, DMTA, and DSC experiments. The properties of the blend greatly depended on the degradation of the PP during grafting. An optimal content of compatibilizer exists, which is dependent on the degradation of PP, grafting yield of oxazoline monomer, and on the amount of free, ungrafted monomer present in the compatibilizer. These factors can be adjusted by properly choosing the processing conditions and chemical parameters. © 1997 John Wiley & Sons, Inc. J Appl Polym Sci 63: 883–894, 1997     

Variability in oil content and fatty acid composition in wild northern currants

Seed oils of wild berries of alpine currant (AC) and northern redcurrant (NRC) were investigated. Oil contents of AC and NRC varied between 4.9 % and 9.7% and between 12.8% and 38.5%, respectively. The proportions of α-linolenic, γ-linolenic and stearidonic acids were higher in NRC (means of 21.7, 12.3 and 5.4%, respectively) than in AC (16.8, 8.6 and 3.0%). The growth areas of NRC can be divided into two distinct groups according to the proportions of different polyunsaturated fatty acids. Oil content of NRC correlated negatively to the proportion of linoleic acid and positively to that of stearidonic acid. There were significant correlations between all polyunsaturated fatty acids in NRC but correlations were less obvious in AC. Interestingly, the correlation between linoleic and γ-linolenic acids was positive in NRC but negative in AC. α-Linolenic and stearidonic acids showed positive correlations in both species. In NRC the synthesis of triunsaturated fatty acids is directed either towards α-linolenic or γ-linolenic acids. Results showed great potential in NRC and AC for plant breeding due to the natural variation in the content and composition of the seed oils for functional nutrients. Received: 20 August 1999 / Revised version: 29 October 1999