Effect of ceramic particle size and applied pressure on time to complete infiltration of liquid aluminium into SiC powder compacts

Monitoring of pressurized advance of liquid aluminium into SiC particle compacts of mean particle sizes 12.8, 22.8 and 36.7 m was carried out under applied pressures of 400 to 900 kPa. Infiltration time of liquid aluminium in the compact was recorded by computer logging the output from pairs of open ended wires with a potential difference between them. Results showed that time necessary to complete infiltration in the compacts decreased with increasing particle size and increasing applied pressure. Experimental results are in reasonably good agreement with model predictions.     

Molecular methods for identification of Lactobacillus delbrueckii subsp. bulgaricus and Streptococcus thermophilus using methionine biosynthesis and 16S rRNA genes

Yoghurt and starter culture producers are still searching strains of Lactobacillus delbrueckii subsp. bulgaricus and Streptococcus thermophilus to produce healthier yogurt with longer shelf life, better texture, taste and quality. However, selective identification of Lb. delbrueckii subsp. bulgaricus and Strep. thermophilus from a mixed population using microbiological and biochemical methods is difficult, time consuming and may not be accurate. In this study, a quick, sensitive and accurate method is proposed to identify both Lb. delbrueckii subsp. bulgaricus and Strep. thermophilus using PCR. The method is comprised of two parts. In the first part, methionine biosynthesis genes, known to be present in both species were partially amplified by designed primers (cysmet2F and cysmet2R). Partial amplification of the methionine biosynthesis gene which gives 700 bp fragment resulted in selective identification of Lb. bulgaricus and Strep. thermophilus. All 16 Lb. bulgaricus and 6 Strep. thermophilus isolates assessed by this method gave the expected amplification. On the other hand, further analysis of other closely related species with the same primers have indicated that the same product was also amplified in two more lactobacilli namely, Lb. delbrueckii subsp. lactis and Lb. helveticus species. Thus, in the second part of the method, further differentiation of Lb. delbrueckii subsp. bulgaricus and Strep. thermophilus from each other and these species was achieved using restriction analysis of 16S rRNA gene with EcoRI.     

Mechanical properties and biocompatibility of plasma-nitrided laser-cut 316L cardiovascular stents

The effect of surface modification of laser-cut 316L cardiovascular stents by low-T plasma nitriding was evaluated in terms of mechanical properties and biocompatibility of the stents. The plasma nitriding was performed at 400, 450 or 500 °C using various ratios of nitrogen–hydrogen gas mixtures. The flexibility and radial strength were measured in crimped and expanded state of the stents, respectively. The mechanical properties could be adjusted and improved by plasma nitriding conducted at temperatures lower than 450 °C and/or nitrogen content less than 10% in the treatment gas. An osteoblast cell culture model system was utilized to investigate the effect of plasma nitriding of the stents on the biological response towards the stents, using biological criteria such as cell viability, alkaline phosphatase and nitric oxide production. In terms of cell viability and alkaline phosphatase production, the plasma nitriding procedure did not appear to negatively affect the biocompatibility of the 316L steel stents. However, in terms of nitric oxide production that was slightly increased in the presence of the plasma-nitrided stents, an indirect improvement in the biocompatibility could possibly be expected.     

Characterization of the drilling alumina ceramic using Nd:YAG pulsed laser

Laser micromachining can replace mechanical removal methods in many industrial applications, particularly in the processing of difficult-to-machine materials such as hardened metals, ceramics, and composites. It is being applied across many industries like semiconductor, electronics, medical, automotive, aerospace, instrumentation and communications. Laser machining is a thermal process. The effectiveness of this process depends on thermal and optical properties of the material. Therefore, laser machining is suitable for materials that exhibit a high degree of brittleness, or hardness, and have favourable thermal properties, such as low thermal diffusivity and conductivity. Ceramics which have the mentioned properties are used extensively in the microelectronics industry for scribing and hole drilling.Rapid improvement of laser technology in recent years gave us facility to control laser parameters such as wavelength, pulse duration, energy and frequency of laser. In this study, Nd:YAG pulsed laser (with minimum pulse duration of 0.5 ms) is used in order to determine the effects of the peak power and the pulse duration on the holes of the alumina ceramic plates. The thicknesses of the alumina ceramic plates drilled by laser are 10 mm. Average hole diameters are measured between 500 μm and 1000 μm at different drilling parameters. The morphologies of the drilled materials are analyzed using optical microscope. Effects of the laser pulse duration and the peak power on the average taper angles of the holes are investigated.     

Methanogenic and sulphate reducing bacterial population levels in a full-scale anaerobic reactor treating pulp and paper industry wastewater using fluorescence in situ hybridisation.

In this study, specific methanogenic activity (SMA) test and fluorescence in situ hybridisation (FISH) were respectively used to determine acetoclastic methanogenic capacity, and composition and number of methanogenic and sulphate reducing bacterial (SRB) populations within a full scale anaerobic contact reactor treating a pulp and paper industry effluent. The sludge samples were collected from three different heights along the anaerobic reactor having a difficulty of completely stirring. Performance of the anaerobic reactor in terms of COD removal efficiency varied between 47 and 55% at organic loading rates in a range of 1.6-1.8 kg COD m(-3) d(-1) and methane yield varied between 0.18 and 0.20 m3CH4kg CODrem(-1). The anaerobic reactor was not operated for 2 weeks during the monitoring period. According to SMA test results, potential methane production rate was 276 mLCH4 gVSS(-1) d(-1) before the off period of the reactor, however it decreased to 159 mL CH4 gVSS(-1) d(-1) after this period. SMA test and FISH results along the reactor height showed that the acetoclastic methanogenic activity of the sludge samples, the relative abundance of acetoclastic methanogens, hydrogenotrophic methanogens and acetate oxidising SRB decreased as the reactor height increased, however the relative abundance of non-acetate oxidising SRB increased.     

Discovering mappings in hierarchical data from multiple sources using the inherent structure

Unprecedented amounts of media data are publicly accessible. However, it is increasingly difficult to integrate relevant media from multiple and diverse sources for effective applications. The functioning of a multimodal integration system requires metadata, such as ontologies, that describe media resources and media components. Such metadata are generally application-dependent and this can cause difficulties when media needs to be shared across application domains. There is a need for a mechanism that can relate the common and uncommon terms and media components. In this paper, we develop an algorithm to mine and automatically discover mappings in hierarchical media data, metadata, and ontologies, using the structural information inherent in these types of data. We evaluate the performance of this algorithm for various parameters using both synthetic and real-world data collections and show that the structure-based mining of relationships provides high degrees of precision.     

Morphological characterization and electrochemical/electrical properties of poly(N‐vinyl carbazole)/montmorillonite composites

A series of poly(N‐vinyl carbazole) (PNVCz)/sodium montmorillonite (Na⁺MMT) and PNVCz/organo‐MMT composite materials have been successfully prepared by in situ free radical polymerization with cerium ammonium nitrate (CAN) as initiator in the presence of inorganic nanolayers of hydrophilic Na⁺MMT or organophilic organo‐MMTs, modified with octadecylamine (ODA) and trimethyl stearyl ammonium (TMSA). The synthesized materials were subsequently characterized by Fourier transform infrared spectroscopy (FTIR), X‐ray diffraction (XRD), and differential scanning calorimetry (DSC). The distribution of MMT layers in the PNVCz matrix was also studied through polarized optical microscope (POM). Their electrochemical and electrical properties were investigated by cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). The results showed that the type of intercalation agent and mixing method was affected on the structures and properties of composite materials. Both the interlayer spacing of clays and glass transition temperature of PNVCz was increased nearly from 1.18 nm to 3.53 nm and from 140°C to 185°, respectively. Their conductivities also increased relatively to that of the PNVCz homopolymer (10⁻¹¹–10⁻¹⁵ S/cm) and varied in the range of 10⁻¹⁰–10⁻⁵ S/cm, inversely dependent on the amount of MMT loading. POLYM. COMPOS., 2011. © 2011 Society of Plastics Engineers     

Evaluation of association between atherogenic index of plasma and intima‐media thickness of the carotid artery for subclinic atherosclerosis in patients on maintenance hemodialysis

Incidence of cardiovascular diseases in the patients having chronic kidney disease (CKD) is between 25% and 60%. This increased rate is proposed to be associated with “accelerated atherosclerosis.” Increased carotid intima‐media thickness (CIMT) is a subclinical atherosclerosis marker. Small‐dense low‐density lipoprotein particles are a strong risk factor for atherosclerosis. It was shown that atherogenic index of plasma (AIP = log(TG/HDL‐c)) is correlated with size of the lipoprotein particles. We investigated the correlation between AIP and CIMT which is a subclinical atherosclerosis marker, in hemodialysis (HD) patients. A total of 62 persons with 31 patients under HD therapy and 31 volunteers were included in the study. In all the participants, CIMT was measured and AIP were calculated. AIP and CIMT values of the participants were compared with blood pressures, lipid profiles and the other risk factors. AIP (0.39 ± 0.32) and CIMT (0.57 ± 0.13) were found significantly higher in the patient group than in the controls (0.04 ± 0.36 and 0.45 ± 0.119, respectively); (P = 0.0001 and 0.0001, respectively). There was a significant correlation between AIP and increased CIMT in the patient group (P = 0.0001, r = 0.430). Among the lipid parameters, the strongest correlation was found between CIMT and AIP. We demonstrated the significant increase of AIP and CIMT in HD patients. A correlation was found between AIP and CIMT. AIP was found to show a correlation with a greater number of risk factors, both classical and CKD specific, than CIMT. These data suggest that AIP might be a method which can be used both in diagnosis of subclinical atherosclerosis and in deceleration processes of its progression.     

Cadmium removal out of human plasma using ion-imprinted beads in a magnetic column

The aim of this study is to utilize ion-imprinted magnetic beads in the selective removal of Cd²⁺ ions out of human plasma overdosed with Cd²⁺ ions. The Cd²⁺ imprinted magnetic poly(HEMA-MAC) (mPHEMAC-Cd²⁺) beads were produced by suspension polymerization in the presence of magnetite Fe₃O₄ in a nano-powder form. The template Cd²⁺ ions could be reversibly detached from the matrix to form mPHEMAC-Cd²⁺ beads using 0.1 M thiourea solution. The specific surface area of the mPHEMAC-Cd²⁺ beads was found to be 24.7 m²/g. The MAC and Fe₃O₄ contents of the mPHEMAC-Cd²⁺ beads were found to be 41.8 µmol/g polymer and 8.2% on the average. The Cd²⁺ adsorption capacity of mPHEMAC-Cd²⁺ columns decreased drastically from 48.8 µmol/g to 20.0 µmol/g as the flow rate is increased from 0.50 ml/min to 3.0 ml/min. The maximum adsorption capacity of the mPHEMAC-Cd²⁺ beads was determined to be 48.8 µmol Cd²⁺/g on the average. The relative selectivity coefficients of the mPHEMAC beads for Cd²⁺/Pb²⁺ and Cd²⁺/Zn²⁺ were 22.6 and 160.7 times greater than those of the non-imprinted magnetic PHEMAC (mPHEMAC) beads, respectively. The mPHEMAC-Cd²⁺ beads are reusable for many times with no significant decrease in their adsorption capacities.