Effect of Bleaching on Roughness of Dental Composite Resins

This study investigated the effect of three bleaching agents (Whiteness Perfect, Whiteness Super, Whiteness HP) on roughness of three dental resin composites (Admira, Durafill VS, Gradia Direct). Twenty disk-shaped standard specimens (10 × 2 mm) of each composite material were prepared and divided into four subgroups (n = 5). In each resin composite group, the unbleached specimens served as control; the other specimens were bleached with one of the bleaching agents according to the manufacturer's instruction. Roughness values were assessed using the atomic force microscope and metallographic microscope. Two-dimensional and 3D images were also taken for detecting surface alterations of each specimen group. Although the surfaces of all specimens did not seem to be smooth, the unbleached control specimens showed more irregular areas compared with those of the bleached ones. Roughness values were decreased in bleached groups to some extent depending on the bleaching agents used.     

Nanofibrous wound dressing material by electrospinning method

Abstract

Wound dressings are very useful materials for accelerating the wound healing process. In this study, nanofibrous wound dressings were produced from blending solution of Poly-lactic acid(PLA)/Chitosan(C)/Starch(S)/Zinc oxide(Z) by electrospinning method. Morphology, chemical interaction, mechanical, water uptake and weight loss tests were performed on each samples. Moreover, the biocompatibility of primary dermal fibroblast (ATCC, PCS-201-012) on prepared wound dressings was investigated with MTT assays in vitro, and the samples were found suitable for cell viability and proliferation. These results suggest that produced nanofibrous wound dressings can be promising candidate for wound dressing applications.     

Time Series Simulation with Randomized Quasi-Monte Carlo Methods: An Application to Value at Risk and Expected Shortfall

Quasi-Monte Carlo methods are designed to produce efficient estimates of simulated values but the error statistics of these estimates are difficult to compute. Randomized quasi-Monte Carlo methods have been developed to address this shortcoming. In this paper we compare quasi-Monte Carlo and randomized quasi-Monte Carlo techniques for simulating time series. We use randomized quasi-Monte Carlo to compute value-at-risk and expected shortfall measures for a stock portfolio whose returns follow a highly nonlinear Markov switching stochastic volatility model which does not admit analytical solutions for the returns distribution. Quasi-Monte Carlo methods are more accurate but do not allow the computation of reliable confidence intervals about risk measures. We find that randomized quasi-Monte Carlo methods maintain many of the advantages of quasi-Monte Carlo while also providing the ability to produce reliable confidence intervals of the simulated risk measures. However, the advantages in speed of convergence of randomized quasi-Monte Carlo diminish as the forecast horizon increases.     

A Study of Complexation-ability of Neutral Schiff Bases to Some Metal Cations

The constants of the extraction equilibrium and the distribution for dichloromethane as an organic solvent having low dielectric constant of metal cations with chiral Schiff bases, benzaldehydene-(S)-2-amino-3-phenylpropanol (I), ohydroxybenzaldehydene-( S)-2-amino-3-phenyl-propanol (II), benzaldehydene-(S)-2- amino-3-methylbutanol (III) with anionic dyes [4-(2-pyridylazo)-resorcinol mono sodium monohydrate (NaPar), sodium picrat (NaPic) and potassium picrat (KPic)] and some heavy metal chlorides were determined at 25 ºC. All the ligands have given strongest complexation for NaPar. In contrast, similar behaviour for both alkali metal picrates is not apparent in the complexation of corresponding ligands.     

Vibration Control of Flexible Manipulators Using Smart Structures

The long reach robots required for space applications necessitate active vibration control algorithms for a better pointing performance. The inherent flexibility of the long and flexible space arms can generate undesirable vibrations, making their end-point controls very difficult, although they provide a large reach volume and payload capabilities. This paper presents a novel technique to control the vibrations of N modes of a flexible link attached to a rigid robot employing an Impedance Control Technique using piezo-ceramic actuators and fiber-optic sensors. A piezo-ceramic actuator model has been developed by considering the moments∕forces generated by the piezo-ceramic actuator as nonconservative external forces. Successful simulation and experimental results have been obtained for vibration control of a cantilever beam which is attached to the end effector of the Titan-II robot arm.     

Statistics for estimating the population average of a Lifshitz–Slyozov–Wagner (LSW) distribution

A generic version of the Lifshitz–Slyozov–Wagner (LSW) distribution is introduced. Using this generic form, a maximum likelihood (ML) estimator for the population average has been developed. The statistical properties of the estimates obtained by the ML method, as well as the conventional sample average method, have been assessed by Monte Carlo simulations for seven sample sizes ranging from 10 to 1000. Results showed that (i) both estimators yield practically unbiased results, (ii) the standard deviation of estimates obtained by the ML method is significantly less than that of the sample averages, (iii) the distribution of estimates is neither normal, lognormal nor 2-parameter Weibull. Percentage points of the distribution of estimates for both methods have been developed. The use of these points for calculating confidence limits for the population average of the LSW distribution is demonstrated by examples in this article.     

Practical Integrated Design Strategies for Opaque and All-Optical DWDM Networks: Optimization Models and Solution Procedures

Dense wavelength division multiplexing (DWDM) opaque networks use expensive optical/electrical/optical (O/E/O) conversion at each end of a fiber link. Several technological advances have been used in an attempt to reduce the O/E/O conversion cost component: improved optical amplifiers using distributed Raman amplification allow signals to traverse longer distances without amplification and/or regeneration; optical switches allow the signal to remain in the optical domain most of the time. Networks that use this equipment to eliminate some of the O/E/O conversions are called transparent or all-optical networks and benefit from reduced capital costs at the expense of operational costs and complexity in order to handle potential adjustments in traffic demand. In this investigation, we develop optimization-based algorithms for DWDM network design and traffic routing for both opaque and all-optical networks. This study compares the performance of AMPL/CPLEX implementations of both algorithms on realistically sized networks with up to 36 nodes and 67 links. In all test cases considered the all-optical network design is substantially less expensive than the traditional opaque network design with cost reductions in the range of 12% to 26%.