Achieving state estimation equivalence for misassigned disturbances in offset‐free model predictive control

Integrated white noise disturbance models are included in advanced control strategies, such as Model Predictive Control, to remove offset when there are unmodeled disturbances or plant/model mismatch. These integrating disturbances are usually modeled to enter either through the plant inputs or the plant outputs or partially through both. There is currently a lack of consensus in the literature on the best choice for the structure of this disturbance model to obtain good feedback control. We show that the choice of the disturbance model does not affect the closed‐ loop performance if appropriate covariances are used in specifying the state estimator. We also present a data based autocovariance technique to estimate the appropriate covariances regardless of the plant's true unknown disturbance source. The covariances estimated using the autocovariance technique and the resulting estimator gain are shown to compensate for an incorrect choice of the source of the disturbance in the disturbance model. © 2009 American Institute of Chemical Engineers AIChE J, 2009     

An electrochemical study of the dissolution of gold in thiosulfate solutions Part I: Alkaline solutions

The anodic dissolution of gold in alkaline thiosulfate solutions has been studied by using a rotating gold disc. Experimental results have shown that the gold dissolves at measurable rates in thiosulfate solutions at potentials above 0.2 V. It has been confirmed that dissolution occurs in parallel with oxidation of thiosulfate with a dissolution current efficiency that varies with time and with the experimental conditions and which is generally in the range of 0.3 to 0.6. Although oxygen could be used as an oxidant for gold in the thiosulfate system, the rate of the cathodic reduction of oxygen in the relevant potential region is too slow for practical purposes. It was found that in the potential region investigated, thiosulfate ions undergo oxidative decomposition leaving a sulfur-like film on the surface of gold, which inhibits the rate of dissolution of gold and results in a low anodic current efficiency for the dissolution of gold. The factors (temperature, pH, thiosulfate concentration and ammonia) have been found to have positive effects on the kinetics of gold dissolution. The rates of gold dissolution in oxygenated alkaline thiosulfate solutions have been estimated to be much lower than in the copper–ammonia–thiosulfate and cyanide systems.     

An electrochemical study of the dissolution of gold in thiosulfate solutions. Part II. Effect of Copper

Thiosulfate has been considered as one of the most promising of the non-toxic alternatives to cyanide for the leaching of gold and much work has been carried out with the aim of understanding and improving the ammoniacal thiosulfate leaching process. In particular the behaviour of gold in thiosulfate solutions containing copper in the absence of ammonia has received little attention. It has been shown in this study involving electrochemical and leaching tests that copper ions catalyze not only the oxidation of thiosulfate but also the dissolution of gold in alkaline thiosulfate solutions. Electrochemical studies have shown that copper has a positive effect on the anodic dissolution of gold with increasing concentrations of copper resulting in higher dissolution rates of gold at a potential of 0.3V. Studies on the dissolution of gold powder in alkaline oxygenated thiosulfate solutions containing low concentrations of copper have shown that the role of copper in enhancing the dissolution rate of gold is possibly associated with the formation of a copper–thiosulfate–oxygen intermediate which is more reactive in terms of cathodic reduction than dissolved oxygen. The electrochemical experiments have been complemented by a leaching study which has shown that milling of gold powder in the presence of copper (added as ions, metal, or oxide) assists with the dissolution of gold in thiosulfate solutions.     

The release of catanionic mixtures embedded in gels: An approximate analytical analysis

We present an approximate analytical analysis of the release of catanionic mixtures from gels. The starting points are the monomer–mixed micelle equilibrium, described by using regular solution theory, and the one‐dimensional diffusion equation. Focusing on a half‐infinite planar system, we first point out an exact reduction of the problem to a system of ordinary differential equations. By using the pseudo‐steady‐state approximation and the integral‐balance method, we then derive a single nonlinear equation for the mole fraction of drug in micelles at the extraction front. This equation may be readily solved numerically (or graphically), and once the solution is found, all quantities of interest may be determined in closed form. Comparisons with numerical solutions of the fully nonlinear problem indicate that the errors resulting from the approximations typically do not exceed 10 %. © 2010 American Institute of Chemical Engineers AIChE J, 2011     

Reduction of a single granule drying model: An essential step in preparation of a population balance model with a continuous growth term

The development of a Population Balance Model (PBM) for a pharmaceutical granule drying process requires a continuous growth term; the latter actually represents the drying process as the moisture content is the internal coordinate of the PBM. To establish such a PBM, a complex drying model for a single granule needs reduction in complexity. The starting point is a detailed model that describes the drying behavior of single pharmaceutical granules. A Global Sensitivity Analysis (GSA) was performed to detect the most sensitive degrees of freedom in the model as these need to be retained in the reduced model. Simulations of the complex drying model were, in a next phase, used to develop the reduced model, which describes the decrease of the moisture content in function of the gas temperature. The developed reduced model was then included in a Population Balance Equation (PBE) to describe the drying behavior of a population of granules. © 2012 American Institute of Chemical Engineers AIChE J, 59: 1127–1138, 2013     

Biodegradable macromolecular conjugates of citropin: Synthesis,characterization and in vitro efficiency study

The effective synthesis of citropin–polymer conjugates was described in this paper. The obtained biodegradable polymeric matrices and polymeric conjugates were characterized using ¹H or ¹³C NMR and Fourier transform infrared spectroscopies, gel permeation chromatography and scanning electron microscopy. Toxicity of polymers was evaluated with bacterial luminescence test and two protozoan assays. The in vitro release study of citropin from the obtained conjugates was investigated. The preliminary results of antimicrobial activity of the obtained macromolecular conjugates against Bacillus anthracis, Enterococcus hirae and Staphylococcus aureus were also discussed. The peptide had a high level of antimicrobial activity during 3–5 weeks of the degradation process. The development of biodegradable citropin systems should be of a great interest in the delivery systems of antimicrobial agents.     

Colon‐specific oral delivery of vitamin B2 from poly(acrylamide‐co‐maleic acid) hydrogels: An in vitro study

Hydrogels, composed of poly(acrylamide‐co‐maleic acid) were synthesized and the release of vitamin B₂ from these gels was studied as a function of the pH of the external media, the initial amount of the drug loaded, and the crosslinking ratio in the polymer matrix. The gels containing 3.8 mg of the drug per gram gel exhibit almost zero‐order release behavior in the external media of pH 7.4 over the time interval of more than their half‐life period (t_1/2). The amount of the drug loaded into the hydrogel also affected the dynamic release of the encapsulated drug. As expected, the gels showed a complete swelling‐dependent mechanism, which was further supported by the similar morphology of the swelling and release profiles of the drug‐loaded sample. The hydrophilic nature of the drug riboflavin does not contribute toward the zero‐order release dynamics of the hydrogel system. On the other hand, the swelling osmotic pressure developed between the gels and the external phase, due to loading of the drug by equilibration of the gels in the alkaline drug solution, plays an effective role in governing the swelling and release profiles. Finally, the minimum release of the drug in the swelling media of pH 2.0 and the maximum release with zero‐order kinetics in the medium of pH 7.4 suggest that the proposed drug‐delivery devices have a significant potential to be used as an oral drug‐delivery system for colon‐specific delivery along the gastrointestinal (GI) tract. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 84: 1133–1145, 2002; DOI 10.1002/app.10402     

Spontaneous Cell Detachment and Reattachment in Cancer Cell Lines: An In Vitro Model of Metastasis and Malignancy

There is an unmet need for simplified in vitro models of malignancy and metastasis that facilitate fast, affordable and scalable gene and compound analysis. “Adherent” cancer cell lines frequently release “free-floating” cells into suspension that are viable and can reattach. This, in a simplistic way, mimics the metastatic process. We compared the gene expression profiles of naturally co-existing populations of floating and adherent cells in SW620 (colon), C33a (cervix) and HeLa (cervix) cancer cells. We found that 1227, 1367 and 1333 genes were at least 2-fold differentially expressed in the respective cell lines, of which 122 were shared among the three cell lines. As proof of principle, we focused on the anti-metastatic gene NM23-H1, which was downregulated both at the RNA and protein level in the floating cell populations of all three cell lines. Knockdown of NM23-H1 significantly increased the number of floating (and viable) cells, whereas overexpression of NM23-H1 significantly reduced the proportion of floating cells. Other potential regulators of these cellular states were identified through pathway analysis, including hypoxia, mTOR (mechanistic target of rapamycin), cell adhesion and cell polarity signal transduction pathways. Hypoxia, a condition linked to malignancy and metastasis, reduced NM23-H1 expression and significantly increased the number of free-floating cells. Inhibition of mTOR or Rho-associated protein kinase (ROCK) significantly increased cell death specifically in the floating and not the adherent cell population. In conclusion, our study suggests that dynamic subpopulations of free-floating and adherent cells is a useful model to screen and identify genes, drugs and pathways that regulate the process of cancer metastasis, such as cell detachment and anoikis.     

An Experimental Model of Neuro–Immune Interactions in the Eye: Corneal Sensory Nerves and Resident Dendritic Cells

The cornea is an avascular connective tissue that is crucial, not only as the primary barrier of the eye but also as a proper transparent refractive structure. Corneal transparency is necessary for vision and is the result of several factors, including its highly organized structure, the physiology of its few cellular components, the lack of myelinated nerves (although it is extremely innervated), the tightly controlled hydration state, and the absence of blood and lymphatic vessels in healthy conditions, among others. The avascular, immune-privileged tissue of the cornea is an ideal model to study the interactions between its well-characterized and dense sensory nerves (easily accessible for both focal electrophysiological recording and morphological studies) and the low number of resident immune cell types, distinguished from those cells migrating from blood vessels. This paper presents an overview of the corneal structure and innervation, the resident dendritic cell (DC) subpopulations present in the cornea, their distribution in relation to corneal nerves, and their role in ocular inflammatory diseases. A mouse model in which sensory axons are constitutively labeled with tdTomato and DCs with green fluorescent protein (GFP) allows further analysis of the neuro-immune crosstalk under inflammatory and steady-state conditions of the eye.     

Effect of hydrothermal aging on dental multilayered zirconia for monolithic restorations: An in vitro study

The aim of this in vitro study was to investigate the changes in mechanical, optical, and surface properties of multilayered zirconia during hydrothermal aging.One conventional block (Katana Zirconia HT) and three multilayered blocks (Katana Zirconia ML, STML, and UTML) of monolithic zirconia were examined. Bar-shaped specimens were autoclaved at 134°C and 0.2MPa for 0, 5, and 10 h. The Young's modulus, three-point flexural strength, and nanoindentation hardness were measured to evaluate the mechanical properties. The surface roughness, phase distribution, surface microstructure, and elemental composition were measured to analyze the surface properties. The contrast ratio and total transmittance were measured via spectrophotometry to evaluate the optical properties. Statistical differences were analyzed using appropriate ANOVA, Tukey HSD post hoc tests, and independent and paired sample t-tests (α = .05).The monoclinic phase increased gradually after hydrothermal aging. The yttrium and zirconium concentrations decreased, and the oxygen concentration and the surface roughness increased in all specimens (P<.05) after the aging process. All specimens showed significant grain push-out and microcracks. The total transmittance increased, and the contrast ratio and Young's modulus decreased in all specimens (P<.05) after the aging process. The nanoindentation hardness and three-point flexural strength exhibited a decreasing tendency after the aging process. However, there were no statistical differences (P>.05) between the materials. Significant interactions between material grades and hydrothermal aging were found for all the properties studied (P<.001).Microstructural alterations and significant phase transformations were detected on the surface of the multilayered zirconia after hydrothermal aging. The hydrothermal aging led to increased surface roughness, opaqueness, and elasticity of multilayered zirconia. The optical, mechanical, and surface properties of multilayered zirconia were influenced by the grade of the material after hydrothermal aging. Careful consideration of the grade of materials is necessary for the appropriate selection of multilayered zirconia ceramics for monolithic restorations.     

Adjusting physicochemical and cytological properties of biphasic calcium phosphate by magnesium substitution: An in vitro study

Biphasic calcium phosphate (BCP) is a highly study bone defect repair material with adjustable degradation, perfect osteoconduction and good osteoinduction. As one of the essential trace elements, magnesium (Mg) possesses the abilities of pro-osteogenesis and pro-angiogenesis. Therefore, Mg doping may further expand the application of BCP in bone defect repair, but few studies focus on promoting the osteogenesis and angiogenesis of BCP simultaneously by Mg doping, and the optimal doping amount of Mg remains to be explored. In this study, the physicochemical and biological properties of BCP scaffold affected by Mg doping were systematically study. Results showed that Mg doping enhanced the sintering of BCP scaffold, resulting in the decrease of degradation rate at the initial soaking period. However, the introduction of Mg damaged the lattice stability of BCP, leading to the increase of BCP degradation rate at the later soaking period. BCP scaffolds with Mg doping content ≥3 mol.% could achieve a long-term sustained release of Mg. The ion microenvironment created by Mg-doped scaffolds was simultaneously conducive to the osteogenic differentiation of stem cells and the enhanced angiogenic activity of endothelial cells. The scaffold doped with 5 mol.% of Mg (Mg5–S) showed the highest efficiency in promoting osteogenic differentiation. Mg-doped BCP scaffolds with a doping content ≥3 mol.%, especially Mg5–S, significantly improved the proliferation and angiogenic differentiation of endothelial cells. Based on these, we believe that the optimal doping content of Mg in BCP is 5 mol.%, and Mg5–S has great application potential in bone defect repair.     

Rapid hemostasis by nanofibers of polyhydroxyethyl methacrylate/polyglycerol sebacic acid: An in vitro / in vivo study

Porous nanofibers were prepared from a combination of polyglycerol sebacate (PGS) and polyhydroxyethyl methacrylate (PHEMA) and loaded with tranexamic acid (TA) using the electrospinning method. The nanofibers were optimized for their morphology, diameter size, porosity, TA loading, release profile and mechanical behavior. Their cytotoxicity was studied based on 3-[4,5-dimethylthiazol-2-yl]-2,5-diphenyl tetrazolium bromide assay on L929 cells. The hemostasis control on a tail-cut model in rats was investigated. The best formulation contained 35% of the total polymers, 20% PGS and 10% TA in proportion to the total polymer quantity. These nanofibers had 64% porosity, 8.59% water sorption and 1.47% weight loss after 28 days with no cytotoxicity on the L929 cells. TA loaded nanofibers showed significantly less bleeding volume compared to the other groups, but no significant difference in bleeding time was seen with the blank nanofibers. In other words, the blank nanofibers alone had a hemostatic effect. TA loaded nanofibers were effective in bleeding control and hemorrhagic situations by reducing bleeding time and volume.     

A cellulose‐based hydrogel as a potential bulking agent for hypocaloric diets: An in vitro biocompatibility study on rat intestine

A number of over‐the‐counter slimming products are currently available on the market. However, there is no scientific consensus over their effectiveness in promoting and sustaining weight loss. The need to develop an alternative dietary supplement for the treatment of obesity and overweight makes attractive a polyelectrolyte cellulose‐based hydrogel, crosslinked through a water soluble carbodiimide, as a potential bulking agent or stomach filler for hypocaloric diets. The hydrogel is envisaged to be administered orally to absorb water in the stomach, thus swelling and giving a sense of fullness, and to be finally expelled by fecal way. To this purpose, a preliminary assessment of hydrogel swelling capacity in distilled water has been performed, and the biocompatibility of the material with respect to intestinal tissues has been evaluated in vitro. The direct contact with the intestinal mucosa in vivo has been simulated by contacting the hydrogel with the jejunum tract of rat intestine, and the capacity of the material to maintain the epithelial barrier integrity has been monitored by means of transepithelial electric resistance measurements and lactate dehydrogenase release assay. The reported results evidence that the hydrogel is well tolerated by the intestinal tissue during the expected time of contact in vivo. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102: 1524–1530, 2006     

Effects of ultrasonic scaling on the optical properties and surface characteristics of highly translucent CAD/CAM ceramic restorative materials: An in vitro study

Esthetic restorations using highly translucent ceramics powered by chairside digital dentistry are becoming popular. The purpose of this in vitro study was to investigate the impact of ultrasonic scaling on the optical and surface properties of highly translucent ceramic materials for digital dentistry. A resin nanoceramic (Lava Ultimate; LU), dual-network ceramic (Vita Enamic; VE), feldspathic ceramic (Vitablocs Mark II; VM), lithium disilicate ceramic (IPS e.max CAD; EX), and high-translucency monolithic zirconia (Rainbow Shine-T; MZ) were evaluated. All specimens were subjected to ultrasonic scaling, and the following data were obtained before and after scaling: color change (ΔE₀₀), translucency parameter, surface gloss, surface roughness, and superficial topography. One-way analysis of variance (ANOVA), repeated-measures ANOVA, and two-way ANOVA were used for intergroup comparisons (all α = 0.05). The mean ΔE₀₀ values were 0.243, 0.48, 1.591, 0.143, and 4.466 for LU, VE, VM, EX, and MZ, respectively, with statistically significant differences among the materials. With regard to Commission Internationale de l'Éclairage (CIE) L*, a*, and b* values, VE, VM, and MZ showed significantly decreased L* values relative to the baseline values. Moreover, MZ showed a significantly increased a* value and a significantly decreased b* value after scaling. Ultrasonic scaling also resulted in significant changes in the surface gloss of the LU, VE, VM, and MZ specimens. Micrographs showed scrapes and surface deterioration after scaling. For all materials, the translucency parameter and the surface roughness showed no significant differences between specimens that were subjected to scaling and those that were not. These findings suggest that ultrasonic scaling MARKEDLY affects the optical properties and surface characteristics of highly translucent computer-aided design and computer-aided manufacturing (CAD/CAM) ceramics. The findings can aid restorative dentists in the selection of appropriate materials and motivate periodontists for performing scaling procedures with due consideration of restorations in esthetically demanding areas.     

Three-month evaluation of a low concentration (6% hydrogen peroxide) experimental bleaching gel containing Tio2 and chitosan: An in vitro study

The study aimed to compare the effectiveness of an experimental gel that contained 6% hydrogen peroxide, titanium dioxide (TiO₂), and chitosan nanoparticles with that of the two bleaching agents that are routinely used and evaluate their effectiveness in a 3-month period. Seventy-two extracted premolar teeth were divided into three groups for the bleaching procedure. TiO₂ and chitosan were added to increase the whitening effect of the low-concentration experimental gel. In group 1, the experimental gel was applied and activated with a D-Light Duo LED device. In group 2, Opalescence Boost PF was applied chemically. In group 3, Philips Zoom was applied and activated with Zoom Advanced Power. The color of the teeth was measured with a Vita Easyshade Advance 4.0 spectrophotometer before the bleaching and 24 hours, 7 days, 14 days, 30 days, and 3 months after final bleaching. The CIEDE2000 color differences (∆E₀₀) and average L*, a*, and b* values were calculated. Effective bleaching was observed in three groups as determined by the initial color at different measurement times (P < .05). Philips Zoom showed a higher value of color change than the other groups at all times. The experimental gel showed a bleaching activity like that of Opalescence Boost PF at all-time measurements. A slight decrease in color change was observed between the first-month measurement and third-month measurement in all groups. A low-concentration experimental gel containing TiO₂ and chitosan provided effective whitening, and the whitened color persisted throughout the 3-month period.