Colloid retention in porous media: mechanistic confirmation of wedging and retention in zones of flow stagnation

A three-dimensional particle tracking model for colloid transport in porous media was developed that predicts colloid retention in porous media in the presence of an energy barrier via two mechanisms: (1) wedging of colloids within grain to grain contacts; (2) retention of colloids (without attachment) in flow stagnation zones. The model integrates forces experienced by colloids during transport in porous media, i.e., fluid drag, gravity, diffusion, and colloid-surface Derjaguin-Landau-Verwey-Overbeek interactions. The model was implemented for a fluid flow field that explicitly represented grain to grain contacts. The model utilized a variable time stepping routine to allow finer time steps in zones of rapid change in fluid velocity and colloid-surface interaction forces. Wedging was favored by colloid: collector ratios greater than about 0.005, with this threshold ratio increasing with decreasing fluid velocity. Retention in flow stagnation zones was demonstrated for colloid: collector ratios less than about 0.005, with this threshold decreasing with increasing fluid velocity. Both wedging and retention in flow stagnation zones were sensitive to colloid-surface interaction forces (energy barrier height and secondary energy minimum depth). The model provides a mechanistic basis for colloid retention in the presence of an energy barrier via processes that were recently hypothesized to explain experimental observations.     

Polynorbornene/MMT nanocomposites via surface-initiated ROMP: synthesis, characterization, and dielectric and thermal properties

Exfoliated polynorbornene (PNBN)/montmorillonite (MMT) nanocomposites were synthesized for the first time by the surface-initiated ring-opening metathesis polymerization. PNBN is one of the challenging materials in low dielectric films for packaging applications in electric–electronic industries. This is the first example of in situ polymerization of NBN within the catalyst intercalated montmorillonite layers using ROMP in different clay loading degrees. The Na–MMT clay was modified with a Quaternary ammonium salt containing ruthenium complex as a suitable catalyst and intercalant as well. Powder X-ray diffraction spectroscopy and transmission electron microscopy analysis indicated that the resultant nanocomposites exhibited exfoliated morphologies with homogeneous clay platelet distribution. Nanocomposite materials were obtained with high thermal degradation temperature and low dielectric constant when compared with pure PNBN. The dielectric constants decreased with the increase in the clay content.     

Multiple bilateral chondromatous hamartomas of the lung. A rare entity mimicking metastatic carcinoma

Multiple chondromatous hamartomas are extremely rare and we have not found any bilateral presentation in the literature. We report the case of a 47-year-old woman presenting with a cough, chest pain and dyspnea. Chest x-ray and computed tomography revealed multiple and bilateral pulmonary nodules. A metastatic carcinoma was considered, but the open lung biopsy revealed a chondromatous hamartoma of the lung. The pathogenesis of hamartomas is discussed and the recent literature is reviewed.     

Selective IgA deficiency and ankylosing spondylitis

A man with an ankylosing spondylitis (AS) and selective IgA deficiency is described. There have been several reports in the literature indicating coexistence of AS with selective IgA deficiency. As it is suggested in the literature, we believe that selective IgA deficiency is a poor prognostic factor in AS.     

Utilization of Refractory Metals and Alloys in Fusion Reactor Structures

In design of fusion reactors, structural material selection is very crucial to improve reactor’s performance. Different types of materials have been proposed for use in fusion reactor structures. Among these materials, refractory metals and alloys having capability to withstand high temperatures and high neutron wall loads have been considered to get high power density in fusion reactors. However, these materials have insufficient technological database and are very expensive compared to steels. In addition to that, except chromium and some chromium alloys they show no low activation property. This study gives an overview of potential of refractory metals and alloys for possible use in fusion reactors.     

Coal-based bottom ash (CBBA) waste material as adsorbent for removal of textile dyestuffs from aqueous solution

A locally available CBBA waste material was used as adsorbent for removal of reactive dyes from synthetic textile wastewater. This study presents the results of our investigation on color removal from synthetic wastewater containing Vertigo Blue 49 (CI Blue 49) and Orange DNA13 (CI Orange 13) by adsorption onto CBBA waste material. The effectiveness of CBBA waste material in adsorbing reactive dyes from aqueous solutions was studied as a function of contact time, initial dye concentration and pH by batch experiments. Leachability of waste material was also evaluated using standard leaching test with deionized water (DIN38414-S4). pH 7 was more favorable for color removal from both Vertigo Blue 49 (CI Blue 49) and Orange DNA (CI Orange 13). Dyestuff adsorption capacities of CBBA for Vertigo Blue 49 and Orange DNA13 were 13.51 and 4.54mg dye/g adsorbent, respectively. The adsorption isotherms for the CBBA can be better described by the Freundlich isotherm. The results showed that the dyestuff uptake process for both dyes followed the second-order kinetics. The bottom ash used in this study is not classified as ecotoxic/hazardous material according to the French proposal for a criterion and evaluation methods of waste ecotoxicity (CEMWE) and the German regulation on Hazardous Waste Classification (HWC).     

Corrosion and wear behaviors of boronized AISI 316L stainless steel

In this study, the effects of a boronizing treatment on the corrosion and wear behaviors of AISI 316L austenitic stainless steel (AISI 316L) were examined. The corrosion behavior of the boronized samples was studied via electrochemical methods in a simulation body fluid (SBF) and the wear behavior was examined using the ball-on-disk wear method. It was observed that the boride layer that formed on the AISI 316L surface had a flat and smooth morphology. Furthermore, X-ray diffraction analyses show that the boride layer contained FeB, Fe₂B, CrB, Cr₂B, NiB, and Ni₂B phases. Boride layer thickness increased with an increasing boronizing temperature and time. The boronizing treatment also increased the surface hardness of the AISI 316L. Although there was no positive effect of the coating on the corrosion resistance in the SBF medium. Furthermore, a decrease in the friction coefficient was recorded for the boronized AISI 316L. As the boronizing temperature increased, the wear rate decreased in both dry and wet mediums. As a result, the boronizing treatment contributed positively to the wear resistance by increasing the surface hardness and by decreasing the friction coefficient of the AISI 316L.     

Field correlation for flat-topped beam in non-Kolmogorov turbulent medium

Absolute field correlation of flat-topped beam in non-Kolmogorov turbulent medium is examined at the receiver plane. The power law exponent increase affects absolute field correlation inversely. It is found that the absolute field correlation decreases when the propagation distance, deviation from the receiver axis, diagonal transverse distance from the receiver point and turbulence strength increase. Beam flatness order increase yields smaller absolute field correlation. For the employed parameters, the flat-topped beam attains higher absolute field correlation when the wavelength and the source size increase.