Colloidal stability-slip casting behavior relationship in slurry of mullite synthesized by the USP method

This study presents the outcome of a research concerning the relationship between the colloidal stability of mullite powders synthesized by the USP (ultrasonic spray pyrolysis) method and its slip casting behavior. The colloidal stability of mullite slurry has been investigated under three different pH conditions (4.5, 8.9 and 10.9) derived from pH-dependent zeta potential (ZP) curves. Employing these pH values, mullite slurries with 50 wt.% solid content were prepared and slip cast. The microstructures of dried and sintered specimens were examined using SEM. It is concluded that the pH significantly influences the stability and in turn the slip casting behavior of the mullite slurry. In order to prepare homogeneous and stable mullite slurry for efficient slip casting it is preferable to utilize a basic rather than an acidic medium. High pH (i.e. 10.9) tends to leads to more closely packed mullite particles resulting in a homogeneous microstructure and greater structural integrity.     

Evaluation of the effect of food and beverages on enamel and restorative materials by SEM and Fourier transform infrared spectroscopy

Objectives To examine different types of restorative materials used in children as well as primary and permanent teeth enamel when affected by erosive foods. Materials and Method Buttermilk, fruit yoghurt, Coca‐cola, fruit juice, Filtek Z‐250, Dyract Extra, Fuji II LC, and Fuji IX and tooth enamel were used. Measurements were performed on 1‐day, 1‐week, 1‐month, 3‐month, 6‐month time periods by using ATR‐FTIR technique and surface of the specimens were examined with SEM. Results Permanent tooth showed the least change among human tooth samples when compared to restorative materials. Among filler materials, the most change was observed in Fuji IX. In terms of beverages the most changes on absorption peaks obtained from spectra were seen on the samples held in Coca‐Cola and orange‐juice. Conclusion The exposure of human enamel and restorative materials to acidic drinks may accelerate the degradation process and so reduce the life time of filler materials at equivalent integral exposure times longer than three months. Clinical Relevance Erosive foods and drinks having acidic potential destroy not only tooth enamel but also restorative materials. Microsc. Res. Tech. 77:79–90, 2014. © 2013 Wiley Periodicals, Inc.     

Multispectral plasmon induced transparency in coupled meta-atoms

We introduce an approach enabling construction of a scalable metamaterial media supporting multispectral plasmon induced transparency. The composite multilayered media consist of coupled meta-atoms with radiant and subradiant hybridized plasmonic modes interacting through the structural asymmetry. A perturbative model incorporating hybridization and mode coupling is introduced to explain the observed novel spectral features. The proposed scheme is demonstrated experimentally by developing a lift-off-free fabrication scheme that can automatically register multiple metamaterial layers in the transverse plane. This metamaterial which can simultaneously enhance nonlinear processes at multiple frequency domains could open up new possibilities in optical information processing.     

Rod- and wire-like morphologies of tin oxide developed with plasma oxidation after electrodeposition

A new manufacturing method has been developed to prepare films composed of Sn-rich SnO₂ wires and rods using electrodeposition and subsequent plasma oxidation of pure Sn. The morphology of Sn-rich tin oxide grains varied significantly depending on the deposition current density. After a DC plasma oxidation process, the Sn, SnO, and SnO₂ phases were obtained as spherical grains when the previous electrodeposition was carried out at 6 A/dm² current density. The wire morphology was obtained only when the electrodeposition current was below 3 A/dm². The film produced at 1.5 A/dm² and then plasma oxidized showed wire morphology with single crystals of SnO₂ that formed in the (110) direction.     

Simulation of inventory systems with unknown input models: a data-driven approach

Stochastic simulation is a commonly used tool by practitioners for evaluating the performance of inventory policies. A typical inventory simulation starts with the determination of the best-fit input models (e.g. probability distribution function of the demand random variable) and then obtains a performance measure estimate under these input models. However, this sequential approach ignores the uncertainty around the input models, leading to inaccurate performance measures, especially when there is limited historical input data. In this paper, we take an alternative approach and propose a simulation replication algorithm that jointly estimates the input models and the performance measure, leading to a credible interval for the performance measure under input-model uncertainty. Our approach builds on a nonparametric Bayesian input model and frees the inventory manager from making any restrictive assumptions on the functional form of the input models. Focusing on a single-product inventory simulation, we show that the proposed method improves the estimation of the service levels when compared to the traditional practice of using the best-fit or the empirical distribution as the unknown demand distribution.     

Investigation of interfacial thermal resistance of hybrid graphene/hexagonal boron nitride

International Journal of Mechanics and Materials in Design - Hybrid graphene/hexagonal boron-nitride (G/h-BN) has shown significant physical properties and has been fabricated recently. Structural...     

Plasma sphingolipids in patients with sickle cell disease: Multiple-site vaso-occlusive crises could be associated with lower sphingolipid levels

Although sickle cell disease (SCD) and its manifestations have been associated with various lipid alterations, there are a few studies exploring the impact of sphingolipids in SCD. In this study, we determined plasma ceramide (Cer) and sphingomyelin (CerPCho) species and investigated their association with the crisis in SCD. SCD patients (N = 27) suffering from vaso-occlusive crisis (VOC) or acute chest syndrome (ACS) were involved in this study. Blood samples were drawn at crisis and later at steady state periods. Clinical history, white blood cell count (WBC), C-reactive protein and lactate dehydrogenase (LDH) levels were recorded. 16:0, 18:0, 20:0, 22:0 Cer and 16:0, 18:0, 24:0 CerPCho were measured via LC–MS/MS. All measured Cer and CerPCho levels of SCD patients at crisis and steady-state were found to be similar. Inflammation-related parameters were significantly higher in patients with ACS compared to single-site VOC. Patients with multiple-site VOC were found to have significantly lower sphingolipid levels compared with those with single-site VOC, at crisis (16, 18, 24 CerPCho and 18, 22 Cer) and at steady-state (24:0 CerPCho and 18 Cer). Our results show that sphingolipid levels in SCD patients are similar during crisis and at steady state. However, lower sphingolipid levels appear to be associated with the development of multiple-site VOC. Since the differences were observed at both crisis and steady-state, sphingolipid level could be an underlying factor associated with crisis characteristics in patients with SCD.