An Overview of First-Order Model Management for Engineering Optimization

First-order approximation/model management optimization (AMMO) is a rigorous methodology for solving high-fidelity optimization problems with minimal expense in high-fidelity function and derivative evaluation. AMMO is a general approach that is applicable to any derivative based optimization algorithm and any combination of high-fidelity and low-fidelity models. This paper gives an overview of the principles that underlie AMMO and puts the method in perspective with other similarly motivated methods. AMMO is first illustrated by an example of a scheme for solving bound-constrained optimization problems. The principles can be easily extrapolated to other optimization algorithms. The applicability to general models is demonstrated on two recent computational studies of aerodynamic optimization with AMMO. One study considers variable-resolution models, where the high-fidelity model is provided by solutions on a fine mesh, while the corresponding low-fidelity model is computed by solving the same differential equations on a coarser mesh. The second study uses variable-fidelity physics models, with the high-fidelity model provided by the Navier-Stokes equations and the low-fidelity model—by the Euler equations. Both studies show promising savings in terms of high-fidelity function and derivative evaluations. The overview serves to introduce the reader to the general concept of AMMO and to illustrate the basic principles with current computational results.     

Biomimetic formation of crystalline bone-like apatite layers on spongy materials templated by bile salts aggregates

Since the trabecular bone exhibit sponge-like bicontinuity there is a growing interest in the synthesis of spongy-like sieves for the construction of bio-active implantable materials. Here, we propose a one step sol–gel method for the synthesis of bicontinuous pore silica materials using different bile salts aqueous mixtures as templates. The influences of the type and amount of bile salt on the synthesis processes are investigated and correlated with the final material morphology. As a final point, their structural properties are interrelated with their ability to induce a bone-like apatite layer in contact with simulated body fluid (SBF). We have confirmed that under specific template conditions, the synthesized material has an open bio-active macropore structure that is blanched in a 3D-disordered sponge-like network similar than those existed in trabecular bone.     

Influence of Long-Distance Bicycle Riding on Serum/Urinary Biomarkers of Prostate Cancer

Herein, we present a study focused on the determination of the influence of long-distance (53 km) bicycle riding on levels of chosen biochemical urinary and serum prostate cancer (PCa) biomarkers total prostate-specific antigen (tPSA), free PSA (fPSA) and sarcosine. Fourteen healthy participants with no evidence of prostate diseases, in the age range from 49–57 years with a median of 52 years, underwent physical exercise (mean race time of 150 ± 20 min, elevation increase of 472 m) and pre- and post-ride blood/urine sampling. It was found that bicycle riding resulted in elevated serum uric acid (p = 0.001, median 271.76 vs. 308.44 µmol/L pre- and post-ride, respectively), lactate (p = 0.01, median 2.98 vs. 4.8 mmol/L) and C-reactive protein (p = 0.01, 0.0–0.01 mg/L). It is noteworthy that our work supports the studies demonstrating an increased PSA after mechanical manipulation of the prostate. The subjects exhibited either significantly higher post-ride tPSA (p = 0.002, median 0.69 vs. 1.1 ng/mL pre- and post-ride, respectively) and fPSA (p = 0.028, median 0.25 vs. 0.35 ng/mL). Contrary to that, sarcosine levels were not significantly affected by physical exercise (p = 0.20, median 1.64 vs. 1.92 µmol/mL for serum sarcosine, and p = 0.15, median 0.02 µmol/mmol of creatinine vs. 0.01 µmol/mmol of creatinine for urinary sarcosine). Taken together, our pilot study provides the first evidence that the potential biomarker of PCa—sarcosine does not have a drawback by means of a bicycle riding-induced false positivity, as was shown in the case of PSA.     

Wood-Derived Tar as a Carbon Binder Precursor for Carbon and Graphite Technology

In addition to the many benefits of coal tar pitch, these materials are known to contain polycyclic aromatic hydrocarbons. For this reason, studies are being developed to elaborate new, ecologically friendly, alternative binders for carbon–graphite technology. This article presents the results of wood tar recovered during thermal degradation of selected types of woods as alternative binders in the manufacture of carbon materials. Two kinds of wood tars obtained from different raw materials were analyzed. Sawdust thermal conversion makes it possible to obtain carbon binders with a lower coking value and quinoline-insoluble matters in comparison to coal tar pitch. These binders produce significantly reduced emissions of polycyclic aromatic hydrocarbons in carbon–graphite technology. Carbon samples manufactured using wood-derived binders with carbon fillers showed similar density and mechanical compression strength values compared to those based on conventional coal tar pitch binders.     

Study of Linkage between Glutathione Pathway and the Antibiotic Resistance of Escherichia coli from Patients’ Swabs

In this work, we focused on the differences between bacterial cultures of E. coli obtained from swabs of infectious wounds of patients compared to laboratory E. coli. In addition, blocking of the protein responsible for the synthesis of glutathione (γ-glutamylcysteine synthase—GCL) using 10 mM buthionine sulfoximine was investigated. Each E. coli showed significant differences in resistance to antibiotics. According to the determined resistance, E. coli were divided into experimental groups based on a statistical evaluation of their properties as more resistant and more sensitive. These groups were also used for finding the differences in a dependence of the glutathione pathway on resistance to antibiotics. More sensitive E. coli showed the same kinetics of glutathione synthesis while blocking GCL (K_m 0.1 µM), as compared to non-blocking. In addition, the most frequent mutations in genes of glutathione synthetase, glutathione peroxidase and glutathione reductase were observed in this group compared to laboratory E.coli. The group of “more resistant” E. coli exhibited differences in K_m between 0.3 and 0.8 µM. The number of mutations compared to the laboratory E. coli was substantially lower compared to the other group.     

Electrical conductivity and tensile properties of block‐copolymer‐wrapped single‐walled carbon nanotube/poly(methyl methacrylate) composites

Poly(methyl methacrylate) (PMMA) composites containing raw or purified single‐walled carbon nanotubes (SWCNTs) are prepared by in situ polymerization and solution processing. The SWCNTs are purified by centrifugation in a Pluronic surfactant, which consists of polyethyleneoxide and polypropyleneoxide blocks. Both the effects of SWCNT purity and non‐covalent functionalization with Pluronic are evaluated. Electrical conductivity of PMMA increases by 7 orders of magnitude upon the integration of raw or purified SWCNTs. The best electrical properties are measured for composites made of purified SWCNTs and prepared by in situ polymerization. Strains at fracture of the SWCNT/PMMA composites are nearly identical to those of the neat matrix. A certain decrease in the work to fracture is measured, particularly for composites containing purified SWCNTs (?31.6%). Fractography and Raman maps indicate that SWCNT dispersion in the PMMA matrix improves upon the direct addition of Pluronic, while dispersion becomes more difficult in the case of purified SWCNTs. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 41547.     

In vitro toxicity evaluation of hydrogel–carbon nanotubes composites on intestinal cells

Composite materials based on carbon nanotubes (CNT) and polymeric hydrogels have become the subject matter of major interest for use as carriers in drug delivery research. The aim of this study was to evaluate the in vitro cytotoxicity of the hydrogel–carbon nanotube–chitosan (hydrogel–CNT–CH) composites on intestinal cells. Oxidized CNT were wrapped with chitosan (CH), Fourier transform infrared (FT‐IR) analysis suggest that oxidized CNT interact with CH. Transmission electron microscopy (TEM) images show a CH layer lying around CNT. Chitosan wrapped CNT were incorporated to poly (acrylamide‐co‐acrylic acid) hydrogels. Swelling behavior in buffers at different pH were evaluated and revealed a significantly lower swelling when it is exposed to a acid buffer solution (pH 2.2). Mechanical properties were evaluated by measurements of elasticity and the material with CNT showed better mechanical properties. The incorporation and liberation of Egg Yolk Immunoglobulin from hydrogel–CNT–CH were also assessed and it revealed an improved performance. To evaluate the effect of these nanocomposites on cellular redox balance, intestinal cells were exposed to hydrogel–CNT–CH composites and antioxidant enzymes were assessed. Cytotoxicity and apoptosis were also evaluated. Hydrogel–CNT–CH composites induce no oxidative stress and there were no evidence of cytotoxicity or cell death. These preliminary findings suggest that hydrogel–CNT–CH composites show improved properties and good biocompatibility in vitro making these biomaterials promising systems for drug delivery purposes. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 41370.     

Recent Advances in the Liquid‐Phase Synthesis of Metal Nanostructures with Controlled Shape and Size for Catalysis

Recent advances in the liquid‐phase synthesis of metal nanostructures of different sizes and shapes are reviewed regarding their catalytic properties. The controlled synthesis of nanostructures is based on the colloid chemistry techniques in the solution, which use organic nanoreactors and a variety of stabilizers. Their catalytic activity and selectivity depend on the particle's shape and size, as shown for Suzuki and Heck coupling, hydrogenations, hydrogenolysis, oxidations, and electron‐transfer reactions. The knowledge of a reaction's structure‐sensitivity relationship is important for the rational catalyst design in view of process intensification. Nanostructures can be used per se and in supported form to meet the requirements of an eventual process.     

Impact of Fe Content in Laboratory-Produced Soot Aerosol on its Composition,Structure, and Thermo-Chemical Properties

Soot aerosol, which is a major pollutant in the atmosphere of urban areas, often contains not only carbonaceous matter but also inorganic material. These species, for example, iron compounds, originated from impurities in fuel or lubricating oil, additives or engine wear may change the physico-chemical characteristics of soot and hence its environmental impact. We studied the change of composition, structure, and oxidation reactivity of laboratory-produced soot aerosol with varying iron content. Soot types of various iron contents were generated in a propane/air diffusion flame by adjusting the doping amount of iron pentacarbonyl Fe(CO)₅ to the flame. Scanning electron microscopy (SEM)/energy-dispersive X-ray spectroscopy (EDX) was combined with cluster analysis (CA) to separate individual particles into definable groups of similar chemical composition representing the particle types in dependence of the iron content in soot. Raman microspectroscopy (RM) and infrared spectroscopy were applied for the characterization of the graphitic soot structure, hydrocarbons, and iron species. For the analysis of soot reactivity, temperature-programmed oxidation (TPO) was used. It is demonstrated that iron is most dominantly present in the form of amorphous Fe (III) oxide crystallizing to hematite α-Fe₂O₃ upon thermal treatment. Iron contaminations do not change the soot microstructure crucially, but Fe(CO)₅ doping of the flame impacts hydrocarbon composition. Soot oxidation reactivity strongly depends on the iron content, as the temperature of maximum carbon (di)oxide emission T _max follows an exponential decay with increasing iron content in soot. Based on the results of the thermo-chemical characterization of laboratory-produced internally mixed iron-containing soot, we can conclude that iron-containing combustion aerosol samples cannot be characterized unambiguously by current thermo-optical analysis protocols.

Copyright 2012 American Association for Aerosol Research     

Bactericidal strontium-releasing injectable bone cements based on bioactive glasses

Strontium-releasing injectable bone cements may have the potential to prevent implant-related infections through the bactericidal action of strontium, while enhancing bone formation in patients suffering from osteoporosis. A melt-derived bioactive glass (BG) series (SiO₂–CaO–CaF₂–MgO) with 0–50% of calcium substituted with strontium on a molar base were produced. By mixing glass powder, poly(acrylic acid) and water, cements were obtained which can be delivered by injection and set in situ, giving compressive strength of up to 35 MPa. Strontium release was dependent on BG composition with increasing strontium substitution resulting in higher concentrations in the medium. Bactericidal effects were tested on Staphylococcus aureus and Streptococcus faecalis; cell counts were reduced by up to three orders of magnitude over 6 days. Results show that bactericidal action can be increased through BG strontium substitution, allowing for the design of novel antimicrobial and bone enhancing cements for use in vertebroplasty or kyphoplasty for treating osteoporosis-related vertebral compression fractures.